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HORSE    IN    MOTION 

AS   SHOWN    BY   INSTANTANEOUS   PHOTOGRAPHY 

WITH   A   STUDY   ON   ANIMAL    MECHANICS 

FOUNDED   ON  ANATOMY   AND    THE    REVELATIONS 
OF    THE    CAMERA 

/.V    WHICH  IS   DEMONSTRATED    THE    THEORY  OP   QUADRUPEDAL   LOCOMOTION 

BY  J.   D.   B.   STILLMAN,  A.M.,   M.D. 


EXECUTED    AND    PUBLISHED    UNDER    THE    AUSPICES    OF 

LELAND    STANFORD 


BOSTON 

JAMES    R.    OSGOOD    AND    COMPANY 
1882 


Copyright,  1SS1, 
BY  LELAND  STANFORD. 


UNIVERSITY  PRESS: 
JOHN  WILSON  AND  SON,  CAMBRIDGE. 


*7 
5 

/e 


PREFACE. 


I  HAVE  for  a  long  time  entertained  the  opinion  that  the  accepted 
theory  of  the  relative  positions  of  the  feet  of  horses  in  rapid  motion 
was  erroneous.  I  also  believed  that  the  camera  could  be  utilized  to 
demonstrate  that  fact,  and  by  instantaneous  pictures  show  the  actual 
position  of  the  limbs  at  each  instant  of  the  stride.  Under  this  con- 
viction I  employed  Mr.  MUYBRIDGE,  a  very  skilful  photographer,  to 
institute  a  series  of  experiments  to  that  end.  Beginning  with  one, 
the  number  of  cameras  was  afterwards  increased  to  twenty-four,  by 
which  means  as  many  views  were  taken  of  the  progressive  move- 
ments of  the  horse.  The  time  occupied  in  taking  each  of  these 
views  is  calculated  to  be  not  more  than  the  five-thousandth  part 
of  a  second.  The  method  adopted  is  described  in  the  Appendix 
to  this  volume. 

When  these  experiments  were  made  it  was  not  contemplated  to 
publish  the  results;  but  the  facts  revealed  seemed  so  important  that 
I  determined  to  have  a  careful  analysis  made  of  them.  For  this 
purpose  it  was  necessary  to  review  the  whole  subject  of  the  loco- 
motive machinery  of  the  horse.  I  employed  Dr.  J.  D.  B.  STILLMAN, 
whom  I  believed  to  be  capable  of  the  undertaking.  The  result  has 
been  that  much  instructive  information  on  the  mechanism  of  the 
horse  has  been  revealed,  which  is  believed  to  be  new  and  of  suffi- 
cient importance  to  be  preserved  and  published. 


IV  PREFACE. 

The  HORSE  IN  MOTION  is  the  title  chosen  for  the  book ;  for  the 
reason  that  it  was  the  interest  felt  in  the  action  of  that  animal  that  led 
to  the  experiments,  the  results  of  which  are  here  published,  though 
the  interest  wakened  led  to  similar  investigations  on  the  paces  and 
movements  of  other  animals.  It  will  be  seen  that  the  same  law 
governs  the  movements  of  most  other  quadrupeds,  and  it  must  be 
determined  by  their  anatomical  structure. 

The  facts  demonstrated  cannot  fail,  it  would  seem,  to  modify  the 
opinions  generally  entertained  by  many,  and,  as  they  become  more 
generally  known,  to  have  their  influence  on  art. 


LELAND    STANFORD. 


PALO  ALTO  FARM,  CALIFORNIA, 
iSSi. 


CONTENTS. 


CHAPTER   I. 

PAGE 

INTRODUCTORY    9 

CHAPTER  .II. 

The  Horse  considered  as  a  Machine.  —  Necessity  of  understanding  its  Construc- 
tion.—  General  Physiological  and  Anatomical  Facts.  —  Architectural  Prin- 
ciples involved  in  the  Construction  of  the  Skeleton.  —  Of  the  Joints.  —  The 
Vertebra.  —  The  Cartilages  and  Ligaments. — The  Muscles,  Voluntary  and 
Involuntary.  —  General  Facts,  Anatomical,  Physiological,  and  Mechanical, 
regarding  the  Muscles.  —  Articular  Ligaments.  —  Tendons.  —  The  Law  of 
Repair  in  Muscles  and  Tendons. —  Relation  of  the  Form  of  Organs  to  their 
Functions.  —  Utility  made  to  conform  to  Beauty  in  the  Form  of  Organized 
Beings 22 

CHAPTER    III. 

Special  Anatomy. —  Necessity  of  Technical  Terms.  —  The  Ilio  spinalis.  —  Defi- 
nition of  Terms. —  Psoas  magnus.  —  Iliacus. — Tensor  Vaginas  Femoris. — 
Sartorius.  —  Pectineus,  Small  Adductor,  etc.  —  Great  Gluteus.  —  Deep  Glu- 
teus.  —  Long  Vastus.  —  Semi-tendinosus.  —  Semi-membranosus.  —  Great  Ad- 
ductor.—  Gracilis. —  The  Adduction  and  Abduction  of  Muscles.  —  Triceps 
Femoris.  —  Gastrocnemii.  —  Automatic  Action  in  the  Hind  Leg.  —  The  Per- 
forans  and  Perforatus  Muscles  and  their  Tendons.  —  Suspensory  Ligament.  — 
Difficulties  in  the  U'ay  of  determining  the  Amount  of  Work  done  by  Muscles. 
—  Elongation  and  Contraction  of  the  Limbs.  —  Interference  and  Stifle  Ac- 
tion.—  The  Action  of  the  Hock  Joint  to  prevent  Interference. — The  Order 
of  Action  in  the  Various  Muscles  of  the  Posterior  Extremity  in  Locomotion  .  35 

CHAPTER    IV. 

The  Comparison  of  the  Anterior  Extremity  to  the  Spokes  of  a  Wheel  considered. 
—  Its  Three  Characters  of  Crutch,  Passive  Tool,  and  Active  Automaton.  — - 
The  Great  Serratus.  —  Its  Double  Character  of  Tendon  and  Muscle.  — 
Centre  of  Motion. — The  Trapesius  and  Yellow  Cord. —  Levator  Angu'.i 


vi  CONTENTS. 

PAGE 

Scapulae.  —  Trachelo  subscapularis,  its  Function  hitherto  unknown.  —  The 
Great  Dorsal  and  Pectoral  as  Propellers.  —  The  Mastoido  humeralis  as  an 
Extensor.  — The  Muscles  of  the  Shoulder-Blade. — The  Pair  of  Muscles  that 
flex  the  Shoulder.  —  The  Function  of  the  Triceps  in  resisting  the  Fall  of  the 
Body  and  in  Locomotion.  —  Function  of  the  Flexors  of  the  Forearm.  —  High 
Action.  —  Obstacles  to  a  Full  Understanding  of  the  Functions  of  the  Loco- 
motive Muscles  removed  by  the  Camera.  — Analysis  of  the  Movements  of  the 
Anterior  Extremity.  —  Mechanical  Points  desirable  in  a  Horse  for  Speed  or 
Strength.  —  Low  Centres  of  Motion.  —  Long  Levers.  —  Comparison  between 
the  Anterior  and  Posterior  Extremities. —  Why  Quadrupeds  rise  from  Recum- 
bent Positions  with  Difficulty.  —  Why  Boxers  and  Others  liable  to  be  placed 
suddenly  on  the  Defence  have  their  Limbs  semi-flexed.  —  Elements  of 
Speed 60 

CHAPTER   V. 

Influence  of  Gravity  constant.  —  Momentum  accelerated. — The  Law  of  Falling 
Bodies  and  its  Application  to  Locomotion.  —  The  nearer  the  Trajectory  of  the 
Centre  of  Gravity  is  to  a  Straight  Line  the  more  perfect  the  Locomotion.  — 
The  Theory  of  Quadrupedal  Locomotion  stated.  —  Analysis  of  the  Run. — 
The  same  in  all  the  Domestic  Animals.  —  The  Bound  of  the  Deer.  — Why  the 
Flexor  Tendons  of  the  Fore  Legs  are  more  liable  to  be  injured  in  the  Run.  — 
What  is  the  Gallop?  —  Objections  of  Artists  answered.  —  Truth  must  prevail 
over  Conventionalism. — The  Canter 83 

CHAPTER   VI. 

The  Leap  not  properly  a  Pace.  —  Action  in  the  Leap  described. — The  Danger 
to  be  apprehended  in  the  Leap.  —  The  Standing  Leap.  —  Correspondence  in 
the  Action  of  the  Horse  in  the  Leap  and  the  Deer  in  the  Bound.  —  Action  in 
the  Trot.  —  Distinction  between  a  Step  and  a  Stride.  —  The  Difficulty  to  be 
encountered  in  increasing  the  Speed  of  Trotters.  —  Difference  in  the  Action  in 
the  Trot  and  the  Run.  —  Difficulty  in  restraining  a  Horse  from  breaking  into 
a  Run  explained. —  Fast  Trotting  cultivated  in  America  in  Thoroughbreds.  — 
Trotting  not  Hereditary,  but  a  Habit.  —  Theory  and  Mechanical  Action  in  the 
Trot.  — The  Action  in  Ambling,  or  "  Pacing."  —  Definition  of  the  Walk  appli- 
cable to  Bipeds,  not  to  Quadrupeds.  —  The  Action  in  the  Walk.  —  The  Action 
in  the  Pace  known  as  Single-Foot IOS 

CHAPTER   VII. 
ILLUSTRATIONS  OF  THE  PACES Il8 


APPENDIX I23 


LIST     OF     PLATES. 


PAGE 

I.    ARRANGEMENT  OF  THE  CAMERAS  FOR  TAKING  THE  ILLUSTRATIONS 

OF  THE  PACES  (Heliotype) Frontispiece 

II.     SKELETON  OF  THE  HORSE,  REFERENCE  PLATE 26 

Colored  ©rafotngs. 

III.  SUPERFICIAL  LOCOMOTIVE  MUSCLES  EXPOSED 36 

IV.  DEEP  LOCOMOTIVE  MUSCLES  SHOWN 38 

V.    THE  HAUNCH,  WITH  THE  GREAT  VASTUS  REMOVED 40 

VI.     INTERNAL  VIEW  OF  THE  MUSCLES  OF  THE  HAUNCH 42 

VII.     INTERNAL  VIEW  OF  THE  MUSCLES  OF  THE  HAUNCH,  WITH  THE  SAR- 

TORIUS  AND  GRACILIS  REMOVED 42 

VIII.    THE  DEEPEST  MUSCLES  OF  THE  HAUNCH  EXPOSED 44 

IX.    POSTERIOR  VIEW  OF  THE  MUSCLES  OF  THE  HAUNCH 46 

X.    VIEW  OF  THE  POSTERIOR  EXTREMITY,  SHOWING  AUTOMATIC  ACTION 

OF   THE   HOCK   AND    STIFLE  JOINTS 48 

XI.    INTERNAL  VIEW  OF  THE  ANTERIOR  EXTREMITY 63 

XII.     SKELETON  OF  THE  HORSE  IN  RUNNING  POSITIONS 74 

XIII.  "MOHAMMED"  RUNNING  (Heliotype) gS 

XIV.  "HATTiE  H."  RUNNING 98 

XV.    "FLORENCE  A."  RUNNING 98 

XVI.     "PHRYNE"  RUNNING 98 

XVII.    "FLORENCE  A."  RUNNING 98 

XVIII.    GREYHOUND  RUNNING 98 

XIX.    GREYHOUND  RUNNING , 98 

XX.    Two  HOUNDS  RUNNING  AT  UNEQUAL  RATES 98 

XXI.     Ox  RUNNING 98 

XXII.     STEER  RUNNING 98 


Vlll 


LIST   OF   PLATES. 


PACE 

XXIII.  DEER  BOUNDING 98 

XXIV.  DEER  BOUNDING 98 

XXV.     CONVENTIONAL  POSITIONS  OF  HORSES  IN  MOTION 102 

XXVI.  CONVENTIONAL  POSITIONS  OF  HOG  AND  DEER  RUNNING      .     .     .  102 

XXVII.     "MOHAMMED"  CANTERING 104 

"XXVIII.     "FRANKIE"  LEAPING  A  HURDLE 106 

XXIX.     "FRANKIE"  LEAPING  A  HURDLE 106 

XXX.     "PHRYNE"  LEAPING 106 

XXXI.     "PHRYNE"  LEAPING 106 

XXXII.     "PHRYNE"  AFTER  LEAPING 106 

XXXIII.  "PHRYNE"  AFTER  PASSING  THE  HURDLE 106 

XXXIV.  STANDING  LEAP 106 

XXXV.     SKELETON  OF  A  HORSE  IN  LEAPING  POSITIONS 106 

XXXVI.     "EDGERTON"  TROTTING  (Hdiotype) 112 

XXXVII.     "ELAINE"  TROTTING 112 

XXXVIII.     "EDGERTON"  TROTTING 112 

XXXIX.     "CLAY"  TROTTING 112 

XL.     "OCCIDENT"  TROTTING 112 

XLI.    WALK  CHANGING  TO  A  TROT 112 

XLII.  A  FOUR-MONTHS'  COLT  BREAKING  FROM  A  TROT  TO  A  RUN    .     .  112 

XLIII.     BREAK  FROM  A  TROT  TO  A  RUN 112 

XLIV.     "PHRYNE"  UNSETTLED 112 

XLV.     "HATTIE  H."  UNSETTLED 112 

XLVI.     Ox  TROTTING 112 

XLVII.     BOAR  TROTTING 112 

XLVIII.     SKELETON  OF  THE  HORSE  IN  TROTTING  POSITIONS 112 

XLIX.     HORSE  PACING,  OR  AMBLING 114 

L.     "SHARON"  WALKING 114 

LI.     Ox  WALKING 114 

LI  I.    Cow  WALKING  IRREGULARLY,  BEING  DRIVEN 114 

LIII.     BOAR  WALKING.     (SEE  PLATE  XLVII.) 114 

LIV.     HORSE  HAULING 114 

LV.     IRREGULAR  HAULING 114 

LVI.     "SHARON,"  SINGLE- FOOT 114 

LVII.-CV.     ILLUSTRATIONS  OF  THE  PACES 118 

CVI.  VIEW  OF  THE  TWENTY-FOUR  CAMERAS  IN  POSITION  (Hdiotype)     .  123 

CVII.  VIEW  OF  THE  BACKGROUND  AND  ARRANGEMENT  FOR  MEASURING 

THE  STRIDES  (Hdiotype) 124 


THE    HORSE    IN    MOTION. 


CHAPTER     I. 

INTRODUCTORY. 

THE  Horse,  of  all  animals,  holds  the  most  important  relations  to 
the  human  family.  Though  the  earliest  traces  of  his  existence  on  the 
globe  are  found  as  fossils  in  North  America,  as  an  historical  char- 
acter he  is  traced  to  Central  Asia  with  the  Caucasian  race.  There 
was  no  representative  of  the  race  living  in  America  at  the  time  of 
the  discovery  of  the  New  World,  but  it  was  introduced  by  Columbus 
and  his  followers,  and  its  descendants  became  feral  on  the  Prairies 
of  North  and  the  Pampas  of  South  America.  They  were  undoubt- 
edly of  Arabian  stock,  through  the  Moors ;  small,  active,  and  hardy. 
Their  descendants  were  very  numerous  in  what  were  the  northern 
provinces  of  Mexico,  previous  to  the  invasion  of  Texas. 

The  genera  were  well  represented  in  Africa  and  the  deserts  of 
Arabia,  but  we  have  no  evidence  that  the  historic  horse  was  known 
in  Africa  before  the  time  of  Rameses  the  Great,  in  the  Eighteenth 
Dynasty,  after  the  wars  with  the  Persians.  Nowhere  in  all  the  tem- 
ples and  tombs  of  Memphis,  Sais,  Abydos,  of  the  First  Empire,  is 
there  a  sculpture  that  could  lead  us  to  infer  that  the  horse  was 
known  to  the  Egyptians  of  that  early  age.  There  are  no  sculptures 
in  India  older  than  the  dawn  of  Buddh,  or  about  five  centuries 
before  our  era.  The  oldest  written  account  of  the  horse  is  found  in 
the  book  of  Job,  and  that  is  a  very  spirited  description  of  a  war-horse; 
and  it  is  probable  that  that  is  the  oldest  of  the  sacred  writings  of 
the  Hebrews,  though  there  is  no  clew  to  the  date  or  origin  of  that 
curious  production. 


10  THE    HORSE    IN    MOTION. 

Though  the  relative  importance  of  the  horse  as  a  factor  in  the 
progress  of  civilization  has  been  reduced  by  the  introduction  of  steam 
in  our  century,  it  cannot  be  forgotten  that  he  has  been  the  con- 
stant companion  of  the  Caucasian  race  in  all  its  migrations,  an  in- 
dispensable ally  in  all  its  conquests,  and  the  most  efficient  agent  of 
its  civilization.  We  have  no  history  that  is  not  interwoven  with  his; 
and  if  by  some  sudden  cataclysm  he  should  be  eliminated,  we  should 
then  be  made  to  realize  how  indispensable  he  still  is  to  our  business 
and  pleasure.  Whatever  concerns  him  will  never  cease  to  interest 
mankind. 

The  interest  in  the  paces  of  the  horse  is  not  new :  it  had  engaged 
the  attention  of  philosophers  from  ancient  times.  Aristotle,  the 
father  of  Philosophy,  thought  it  not  unworthy  his  investigation  ;  but 
with  all  other  rational  questions,  it  was  lost  to  human  thought  dur- 
ing the  long  reign  of  religious  bigotry.  When  the  intellects  of  men 
were  again  set  free,  and  Science  woke  from  her  slumber,  Anatomy 
was  studied  and  taught  in  the  schools,  and  attention  became  directed 
to  that  of  our  subject ;  but  even  Borelli,  who  wrote  about  two  hundred 
years  ago,  and  published  the  work  on  Animal  Mechanics  that  most 
later  writers  have  drawn  upon,  thought  it  necessary  that  he  should 
not  confound  flesh  and  muscle.  Vital  force  was  as  yet  unknown, 
and  all  treated  the  subject  as  a  physical  science,  and  deduced  its 
laws  from  the  motions  of  the  pendulum,  and  mathematically  formu- 
lated them. 

Two  brothers,  named  Weber,  who  are  quoted  much  by  the  author  of 
"Animal  Motion,"  in  the  "Encyclopaedia  of  Anatomy  and  Physiology," 
followed  Borelli  on  the  purely  physical  theory  of  Animal  Motion. 

Professor  Marey  has  contributed  the  result  of  many  laborious  and 
painstaking  experiments  on  the  slow  paces,  by  means  of  apparatus 
attached  to  the  feet,  and  connected  by  elastic  tubes  with  registers  in 
the  hands  of  the  rider.  This  apparatus  would  determine  the  force 
of  the  footfalls  and  time  of  pressure,  and  by  the  system  of  notation 
a  chart  could  be  made  of  the  paces.  But  it  failed  to  interpret  the 
paces  correctly,  or  furnish  the  basis  of  a  theory  of  quadrupedal  loco- 
motion. The  importance  of  the  subject  had  been  fully  appreciated  by 


THE    HORSE    IN    MOTION.  II 

him,  as  appears  in  the  following  quotation  from  his  work  on  Animal 
Mechanics :  "  There  is  scarcely  any  branch  of  animal  mechanics 
which  has  given  rise  to  more  labor  and  greater  controversy  than  the 
question  of  the  paces  of  the  horse.  The  subject  is  of  great  impor- 
tance to  a  large  number  of  persons  engaged  in  special  pursuits,  but 
its  extreme  complexity  has  caused  interminable  discussion.  Any  one 
who  proposed  at  the  present  time  to  write  a  treatise  on  the  paces  of 
the  horse  would  have  to  discuss  many  different  opinions  put  forward 
by  a  great  number  of  authors." 

Bishop,  the  author  of  the  article  on  "Animal  Motion"  in  the 
"Encyclopaedia  of  Anatomy  and  Physiology,"  says:  "The  study  of 
the  mechanism  of  which  the  locomotive  organs  of  animals  is  com- 
posed, of  the  laws  by  which  their  progression  is  accomplished,  and  of 
the  vital  force  which  they  expend  in  propelling  the  body  from  one 
point  in  space  to  another  with  different  velocities,  serves  to  interest 
alike  the  anatomist  and  the  physiologist,  the  artist  and  the  mechani- 
cian. Ignorance  of  these  laws  has  been  productive  of  grotesque 
delineations  of  the  human  figure  as  well  as  of  the  lower  animals,  when 
represented  in  motion.  We  have  abundant  evidence  of  this  in  the 
productions  of  painters  and  sculptors,  both  of  the  ancient  and  modern 
world." 

The  difficulty  in  this,  as  in  many  controverted  questions,  is  to 
determine  the  facts;  and  the  facts  have  been  most  difficult  to  obtain. 
It  seems  to  many  unaccountable,  that  the  horse,  whose  movements 
are  so  open,  should  play  such  a  leger-de-pied  as  to  deceive  all  eyes, 
and  give  rise  to  controversies  as  earnest  as  did  the  colors  of  the  cha- 
meleon in  the  fable.  All  attempts  hitherto  made  to  analyze  these 
movements  have  failed,  for  it  is  not  possible  for  the  eye  to  distinguish 
them ;  or  rather,  to  state  the  case  more  accurately,  the  mind  is  unable 
to  distinguish  the  impressions  conveyed  to  it  through  the  eye. 

Controversies  were  going  on  to  the  last  as  to  which  foot  was  ad- 
vanced first  in  the  trot ;  whether  the  toe  or  heel  first  touched  the 
ground ;  whether  in  a  gallop  the  legs  were  stretched  out  fore  and  aft, 
or  the  knees  were  flexed.  All  were  dabbling  in  the  shallow  waters 
of  a  sea  whose  depths  there  was  no  known  method  of  exploring,  and 


12  THE    HORSE    IN    MOTION. 

artists  of  all  degrees  fell  into  the  false  and  conventional  manner  of 
representing  animals  in  rapid  motion,  as  untrue  as  were  the  Greek 
conceptions  on  the  subject  thirty  centuries  ago.  To  understand  how 
little  progress  has  been  made  in  modern  times,  it  is  only  necessary  to 
look  at  the  productions  of  the  best  animal  painters  of  our  day. 

Why  is  it  that  there  have  been  such  widely  different  interpre- 
tations of  these  movements  from  the  time  of  Aristotle  down  to  the 
present  ?  These  positions,  as  well  as  all  others  that  have  been  rep- 
resented, are  proved  by  the  unerring  finger  of  light  to  be  incorrect ; 
as  mechanical  anatomy,  had  it  been  properly  consultec1.,  would  have 
demonstrated  to  be  impossible. 

It  is  difficult  at  a  glance  to  conceive  how  the  eye  could  be  so 
deceived ;  but  a  little  consideration  of  the  physiology  of  that  organ 
will  teach  us  that  no  dependence  can  be  placed  on  it  to  interpret  the 
motion  of  an  object  moving  irregularly,  even  at  a  comparatively  slow 
rate  of  speed. 

It  has  been  shown  that  the  retina  of  the  eye  is  capable  of  receiv- 
ing a  distinct  image  of  an  object  in  an  almost  inconceivably  short 
space  of  time,  as  that  of  the  flash  of  an  electric  spark,  or  a  millionth 
part  of  a  second,  and  that  the  impression  remains  for  the  space  of  a 
third  to  a  seventh  of  a  second,  according  to  the  experiments  of  D'Arcy 
and  Plateau  ;  and  the  mind  is  incapable  of  distinguishing  between 
the  first  impression  and  the  last  made  during  that  space  of  time,  and 
the  images  run  together  and  are  confused.  A  familiar  illustration  of 
this  phenomenon  is  furnished  by  the  spokes  of  a  wheel  in  motion ;  yet 
these  spokes  will  appear  stationary,  if,  revolving  in  the  dark,  they  are 
suddenly  illuminated  by  an  electric  flash  ;  or  if  the  end  of  a  stick  be 
ignited,  and  moved  rapidly,  a  continuous  line  of  fire  will  appear.  Here 
there  is  a  continuous  line  of  impressions  made  upon  the  retina,  and  so 
conveyed  to  the  mind.  The  same  is  true  of  the  auditory  nerve ;  when 
vibrations  of  air  are  too  rapid,  they  are  heard,  but  not  distinguished. 
The  reader  may  ask  why  it  is  that  the  artists  of  all  time,  with  the  full 
accord  of  all  men,  —  and  our  own  eyes  confirm  the  tradition, —  represent 
the  horse  in  galloping  as  extending  his  feet  to  the  utmost,  as  seen  in 
all  the  pictures  of  horses  racing.  My  answer  is  this :  We  now  know 


THE    HORSE    IN    MOTION.  13 

that  it  is  not  true  that  a  horse  ever  did  put  himself  in  the  position 
portrayed  by  the  best  artists ;  and  the  explanation  that  I  have  to  offer 
is,  that  in  the  gallop  the  horse  always  moves  his  feet  alternately,  and 
to  the  same  extent;  at  the  limit  of  extension  there  is  a  change  of 
direction  given  to  them,  nnd  their  image  dwells  longer  upon  the  retina, 
and  the  impressions  are  more  lasting  than  of  the  intermediate  and 
more  rapid  movements  which  the  mind  is  unable  to  distinguish  any 
more  than  the  order  in  which  they  are  made. 

The  ear  has  been  relied  upon  to  determine  by  the  rhythm  of  the 
footfalls  the  order  in  which  the  feet  strike  the  ground ;  and  bells  have 
been  attached  to  the  feet,  each  giving  a  different  sound.  Others  have 
studied  the  footprints,  and  the  feet  have  been  differently  shod  to  dis- 
tinguish the  impression  made  by  each  foot  upon  the  ground. 

The  study  of  the  mechanical  anatomy  of  the  horse  is  a  necessity  in 
order  to  a  proper  understanding  of  the  forces  employed  and  their 
combined  action.  This  necessity  has  now  become  more  imperative, 
as  the  action  is  better  understood  from  the  revelations  of  the  camera. 

All  the  systematic  works  on  the  anatomy  of  the  horse  have  followed 
the  plan  of  those  on  human  anatomy,  and  apparently  for  the  same  pur- 
pose, namely,  the  intelligent  treatment  of  the  diseases  and  accidents  to 
which  horses,  as  well  as  men,  are  liable,  while  the  action  and  relation 
of  the  machine,  as  such,  have  been  treated  as  of  secondary  importance 
or  altogether  neglected.  It  has  not  been  possible  to  study  the  action 
of  the  muscles  singly  without  falling  into  errors ;  the  correlation  of 
all  of  them  is  necessary  to  the  understanding  of  any  one.  It  is  to  this 
cause  that  so  many  errors  and  contradictions  found  in  all  authorities 
that  have  been  consulted  are  to  be  ascribed.  Indeed,  how  was  it  pos- 
sible that  it  should  have  been  otherwise,  so  long  as  it  was  not  known 
what  those  actions  were  ? 

The  progressive  motions  of  a  quadruped,  which  must  be  considered 
as  a  unit,  are  very  complex ;  when  so  studied  it  will  be  found  that  all 
the  parts  are  mutually  dependent,  that  the  forces  employed  are  com- 
pound and  often  indirect,  and  that  the  compensation  of  one  indirect 
action  may  be  found  quite  remote.  When  thus  considered  it  will  be 
found  that  the  horse  in  motion  is  as  perfectly  harmonious  in  the  dis- 


14  THE   HORSE   IN   MOTION. 

play  of  his  forces  and  their  balance  as  a  steam  hammer,  which  may  be 
adjusted  to  a  force  sufficient  to  forge  a  shaft  for  an  ocean  steamer  or 
to  crack  a  nut. 

It  cannot  be  expected  that  many  of  those  persons  who  are  inter- 
ested in  the  movements  of  the  horse  will  be  familiar  with  the  anatomi- 
cal terms  necessary  to  be  used  in  the  description  of  the  simplest 
motion,  and  it  cannot  be  made  intelligible  without  them ;  much  less 
can  it  be  expected  that  one  will  be  able  to  comprehend  a  full  stride 
from  any  analysis  that  can  be  given  without  such  knowledge. 

The  writer  thinks  himself  warranted  in  the  assertion  that  the  correct 
interpretation  of  the  mechanical  action  of  the  horse  cannot  be  obtained 
from  any  existing  work.  It  is  very  desirable  that  it  should  be  under- 
stood by  every  one  who  is  interested  in  his  achievements,  and  by  artists 
as  well.  To  facilitate  this  study,  technical  terms  will  be  emitted  as  far 
as  possible,  and  where  they  are  employed  they  will  be  accompanied  by 
popular  ones  as  far  as  they  are  known. 

One  of  the  sources  of  difficulty  to  the  non-professional  student  is 
the  distinctive  names  given  to  different  tissues  whose  mechanical 
function  is  the  same.  Whether  a  muscle  has  its  termination  in  facia 
aponeurosis  or  at  the  bone  on  which  it  acts,  either  directly  or  in- 
directly, may  be  important  to  the  anatomist  or  surgeon ;  but  to  those 
who  desire  to  understand  the  mechanical  action  it  is  a  matter  of  indif- 
ference, very  perplexing,  and  a  fatal  bar  to  the  comprehension  of  the 
subject ;  to  such  it  is  of  little  consequence  whether  the  action  is  direct 
by  muscular  attachments  to  bones,  or  indirect  through  facia  or  other 
fibrous  tissue.  In  all  cases  I  shall  use  such  terms  as  will  most  cor- 
rectly give  my  meaning  in  the  interpretation  of  their  action. 

Another  source  of  confusion  in  the  study  of  the  muscles  of  mo- 
tion in  quadrupeds  is  the  conflicting  names  given  to  them.  When, 
on  the  restoration  of  the  cultivation  of  science,  comparative  anatomy 
began  to  attract  the  attention  of  naturalists,  human  anatomy  had 
already  received  much  attention,  and  names  had  been  bestowed  upon 
all  the  principal  organs.  Some  of  them  were  purely  fanciful ;  others 
were  based  on  their  resemblance  to  other  objects.  The  muscles  were 
often  named  from  their  supposed  function,  or  their  correspondence  to 


THE    HORSE    IN    MOTION.  15 

muscles  found  in  the  human  body.  This  last  has  been  the  most  fruit- 
ful source  of  confusion,  and  the  mind  of  the  student  is  constantly 
biassed  by  this  correspondence  of  names  to  muscles  that  do  not  have 
corresponding  functions.  It  may  be  taken  for  granted  that  organs 
have  the  same  diversity  of  form  in  man  and  animals  as  there  is 
diversity  of  function,  and  in  each  the  organisms  are  just  such  as  best 
serve  the  offices  which  they  were  designed  to  perform.  Some  of  the 
later  authorities  have  attempted  a  reform  in  the  nomenclature  of  the 
muscles,  based  on  their  supposed  uses,  and  have  only  added  to  the  pre- 
vious contusion.  Adductors  and  abductors  have  been  so  multiplied 
that  it  would  seem  that  a  horse,  like  a  crab,  was  made  to  go  sidevvise. 

Anatomy  will  be  treated  no  further  than  is  necessary  to  demonstrate 
locomotion ;  and  those  who  would  pursue  it  further,  and  those  who 
would  be  more  minute  in  their  knowledge  of  structure,  must  dissect 
for  themselves. 

The  writer  has  already  had  occasion  to  allude  to  design,  and  will 
have  frequent  necessity  for  doing  so  in  describing  the  complicated 
mechanism  by  means  of  which  locomotion  in  the  higher  orders  of 
animals  is  effected,  and  he  wishes  it  understood  that  he  uses  that  term 
in  its  literal  and  highest  signification.  He  does  not  shrink  from  the 
use  of  terms  that  imply  an  intelligent  Creator  and  all-pervading  Spirit, 
who,  from  the  beginning,  established  the  foundations  of  the  earth,  and 
who,  in  incomprehensible  wisdom  and  power,  has  fixed  the  laws  which 
govern  the  organic  world  from  the  beginning  through  all  its  changes. 

In  using  the  term  "  higher  orders  of  animals,"  he  follows  custom.  If 
that  distinction  is  founded  on  the  complexity  of  his  locomotive  powers 
or  organization,  then  man  could  not  justly  claim  the  first  rank;  for  if 
his  preservation  had  depended  upon  his  speed  in  locomotion,  he  would, 
in  the  long  struggle  for  life  through  which  he  must  have  passed,  have 
taken  his  place  in  the  earliest  paleontological  deposits. 

It  may  seem  presumptuous  to  compare  objects,  the  lowest  of  which 
are  beyond  our  comprehension.  The  finite  cannot  comprehend  the 
infinite ;  there  must  be  a  limit,  in  the  nature  of  things,  to  all  inquiry 
into  the  phenomena  of  life.  If  physical  science  could  determine  the 
laws  of  that  which  is  hyperphysical,  then  to  its  court  we  might 


1 6  THE    HORSE    IN    MOTION. 

carry  all  cases  involving  ethical  or  aesthetical  questions,  and  form 
might  be  confounded  with  color.  To  this  pans  asinorum  all  the  old 
writers  on  animal  mechanics  came.  They  would  test  vital  force  by  the 
laws  governing  the  motion  of  the  pendulum  or  those  of  gravity.  If 
physical  science  could  establish  the  laws  and  solve  all  the  questions 
that  arise  in  the  investigation  of  vital  phenomena,  and  algebraic  expres- 
sions could  represent  the  unknown  quantities,  the  task  would  be  easy. 
We  could  calculate  the  force  of  the  right  arm  of  a  warrior  as  we  could 
the  weight  of  his  sword ;  but  when  that  arm  descends,  it  falls  with 
more  than  the  force  of  gravity.  There  is  a  power  that  must  enter  into 
all  our  estimates  of  vital  force,  and  that  is  the  will.  It  cannot  be 
ignored  in  any  calculation  on  animal  motion  ;  and  yet  who  can  estimate 
it,  weigh  it,  and  formulate  it,  as  in  the  exact  sciences  ? 

Thomas  Starr  King  used  to  tell  a  story  of  a  countryman  who 
attracted  the  attention  of  a  traveller  by  the  fine  physical  development 
he  displayed,  and  of  whom  he  inquired  his  weight.  "  Well,  stran- 
ger," said  he,  "  ordinarily  I  weigh  two  hundred  and  thirty  pounds,  but 
when  I  am  mad  I  weigh  a  ton." 

The  progress  that  science  has  made  in  every  department,  and  is 
still  making,  is  wonderful,  and  who  can  say  where  it  will  end  ?  But  in 
the  knowledge  of  the  laws  which  govern  the  origin  of  life,  the  vital 
organs  and  their  functions,  of  the  nature  of  that  force  by  which  one 
form  becomes  altered  or  modified  by  the  altered  conditions  of  its  life, 
it  has  made  no  progress  since  the  days  of  Job. 

The  whole  question  of  life  and  vital  force  is  still  a  great  mystery, 
although  it  is  receiving  at  this  time  the  concentrated  attention  of  the 
most  intelligent  naturalists  of  all  nations.  There  are  not  many  who 
deny  that  organic  forms  may  be  modified  within  certain  limits  by  arti- 
ficial means.  There  are  many  who  believe  that  all  organic  beings,  of 
whatever  nature,  had  their  origin  in  the  most  rudimentary  element,  as 
a  cell  possessing  certain  inherent  tendencies  to  develop  by  aggregation 
into  other  and  higher  forms,  unequally  modified  in  various  ways  by 
surrounding  influences,  with  a  tendency  to  variation  by  imperceptible 
degrees  in  every  direction,  the  useful  variations  favoring  the  existence 
of  the  individuals  possessing  them.  This  idea  has  become  familiar 


THK    HOKSK    IN    MOTION  I"] 

under  the  terms  "  natural  selection"  and  "survival  of  the  fittest."  This 
hypothesis  docs  not  presuppose  design,  and  denies  a  Creator.  Under 
the  name  of  "  Darwinism"  it  has  become  popular  and  invaded  all  ranks. 
It  found  the  soil  of  Germany  especially  fitted  for  the  propagation  of  a 
theory  of  such  an  atheistic  character,  and  it  was  proposed  at  a  meeting 
of  the  Society  of  Naturalists  at  Munich,  a  few  years  ago,  to  teach  it  in 
the  national  schools.  It  has  become  so  generally  diffused  in  our  own 
scientific  circles  that  a  reference  to  a  Supreme  Being  in  an  essay  read 
before  a  society  of  naturalists  would  be  considered  to  be  a  poetic  license, 
if  one  had  the  courage  to  make  it;  and  nature  is  usually  personified  to 
meet  the  necessity.  We  have  long  been  familiar  with  the  reference  to 
the  laws  of  nature,  and  we  now  begin  to  hear  of  the  laws  of  evolution. 
In  all  ages  there  has  been  a  tendency  on  the  part  of  the  masses  to 
follow  some  leader  whom  they  desired  to  do  their  thinking  for  them ; 
to  pin  their  faith  to  his,  or  what  they  supposed  to  be  his:  it  is  no  less 
so  in  the  scientific  circles  than  in  the  religious.  Dogmatism  seems  to 
be  leaving  the  latter  to  attach  itself  to  the  former;  at  all  events,  it  is 
inherent  in  the  human  mind;  no  person  is  utterly  free  from  it;  and  to 
appeal  to  the  opinions  of  those  whom  we  believe  to  be  better  informed, 
rather  than  to  examine  the  foundations  of  those  opinions,  has  been 
the  vice  of  all  ages. 

It  is  well  known  that  faculties  and  functions  are  strengthened 
by  use  and  weakened,  or  altogether  lost,  by  disuse.  We  shall  look 
in  vain  for  proofs  of  an  organ  changed  in  the  mechanical  principle 
of  its  construction,  or  one  evolved  by  imperceptible  degrees  where 
none  existed  before;  but  we  shall,  on  the  other  hand,  find  proofs 
in  anatomy  that  the  changes  could  not  have  been  gradual.  Every 
stable-boy  knows  that  qualities  are  transmitted  by  heredity,  and  that 
desirable  ones  may  be  bred  by  judicious  crossing  within  certain  lim- 
its; and  he  knows  as  much  as  any  one  of  the  force,  or  influence,  by 
means  of  which  this  is  brought  about.  Speculation  should  not  be  con- 
founded with  science,  as  was  said  by  Virchow,  or  science  will  lose  its 
claim  to  the  respect  of  mankind  ;  and  this  whole  question  of  evolution 
is  speculative  when  carried  beyond  proof;  and  science,  when  it  crosses 
the  vital  boundary-line,  is  lost  in  speculation.  We  know  that  organic 


1 8  THE   HORSE    IN    MOTION. 

matter  is  subject  to  physical  laws  like  other  matter:  it  is  attracted 
by  the  earth,  and  will  fall  with  a  force  as  great  as  if  it  were  inanimate, 
and  is  equally  subject  to  the  law  of  falling  bodies;  it  acquires  mo- 
mentum, and  its  momentum  is  equal  to  the  weight  multiplied  by 
the  velocity,  the  same  as  that  of  a  railway-car,  or  a  cannon-shot ; 
and  when  vitality  leaves  it,  it  is  resolved  to  its  original  elements, 
oxygen,  carbon,  etc.,  which  the  chemist  can  prove  by  analysis.  But 
has  the  most  skilful  chemist  ever  been  able  by  synthesis  to  restore 
the  lost  element,  the  vital  spark  ?  Has  he  ever  been  able  to  imitate 
the  products  of  that  vital  laboratory  the  stomach,  and  form  the 
aliment  that  replenishes  the  blood? 

With  all  the  knowledge  of  physics  ever  acquired  by  man,  can  he 
make  a  pump  so  perfect  as  the  heart,  —  that  organ  that  forces  the 
blood  loaded  with  fresh  sustenance  to  every  part  of  the  body  ?  And 
what  does  he  know  of  that  power  that  has  kept  it  in  alternate  action 
and  rest  every  instant  since  before  the  earliest  memories  of  his  child- 
hood ? 

He  has  been  familiar  with  the  laws  of  optics  for  centuries,  and  has 
made  instruments  of  glass  and  metal,  in  imperfect  imitation  of  the  eye 
of  an  animal,  to  exalt  the  powers  of  his  own  vision ;  but  what  would 
not  an  optician  give  to  be  able  to  construct  a  concentric  achromatic 
lens,  with  automatic  power  to  adapt  itself  to  the  distance  of  objects, 
such  as  the  eye  of  the  lowest  of  the  vertebrates  ? 

Acoustics  is  another  of  the  physical  sciences  of  which  man  is  a  pro- 
fessor, and  he  has  just  invented  an  instrument  by  means  of  which  he 
can  communicate  in  ordinary  vocal  sounds  to  a  person  miles  distant. 
He  has  recently  invented  another,  by  which  he  can  register  and  pre- 
serve the  intonations  of  his  voice  to  be  returned  to  him  at  will  at  any 
future  time  ;  but  that  most  wonderful  instrument,  the  ear,  he  can  only 
wonder  at  and  admire.  Without  it  the  world  would  be  without  music, 
voice,  or  sound ;  the  faculty  of  speech,  our  consciousness,  memory, 
imagination,  affection  —  but  it  is  needless  to  multiply  this  class  of 
facts.  In  nothing  does  man  show  himself  to  be  the  creation  of  an 
intelligent  power  more  than  in  his  own  creative  faculty.  How  great 
have  been  his  achievements  in  mechanics !  But  what  comparison  does 


THE   HORSE   IN    MOTION.  ig 

the  highest  bear  to  the  locomotive  apparatus  or  machinery  of  the  horse, 
with  its  compound  system  of  levers,  pulleys,  tendons,  springs,  and  mus- 
cular powers,  and. that  marvellous  ingenuity  in  arrangement  to  produce 
results  which  man  has  not  been  able  to  understand  until  now,  and  all 
set  in  motion  through  telegraphic  communication  distributed  to  every 
muscular  fibre,  and  the  whole  of  this  complicated  system  of  organs 
co-ordinated  and  controlled  by  one  central  will  ?  Another  incompre- 
hensible mystery  of  life  is,  that  this  complicated  machine  should  pos- 
sess the  power,  not  only  to  preserve  and  protect  itself  through  a  long 
life,  but  of  reproducing  from  generation  to  generation  indefinitely, 
and  transmitting  to  posterity  its  own  peculiarities  of  form  and  mental 
qualities  ! 

Does  the  whole  organic  world  furnish  no  proofs  of  intelligence  and 
design,  that  we  must  be  told  that  all  these  marvellous  manifestations  of 
both  are  but  the  inherent  properties  of  matter, 

"  And  that  were  true  which  nature  never  told  "? 

If  it  were  an  "  attainment  and  an  aim  "  to  escape  moral  responsibility 
by  getting  rid  of  a  creator,  do  we  approach  any  nearer  the  solution 
of  the  question  of  the  origin  of  life  by  removing  it  farther  off  into  the 
mytho-geologic  eras  ?  Or  is  the  difficulty  in  any  way  diminished  by 
attributing  to  matter  all  the  high  intellectual  functions  that  have  been 
by  unschooled  people  in  all  ages  ascribed  to  supernatural  powers  ? 

Can  the  microscopist,  when  he  discovers  vibriones  in  a  vegetable 
infusion,  or  protoplasm  in  a  drop  of  serum,  be  excusable  for  running 
naked,  like  the  philosopher  of  Syracuse,  through  the  streets,  shouting 
"  Eureka  "  ?  Can  one  who  finds  a  shingle  or  a  brick  claim  that  he  has 
discovered  the  cause  of  a  house  ?  Let  him  account  for  the  origin  of  the 
brick  and  the  shingle  ! 

Because  a  fossil  skeleton  of  a  four-toed  horse,  which  failed  to  con- 
nect his  species  with  our  time,  has  been  found  in  the  fossiliferous 
deposits  of  the  interior  of  this  continent,  does  it  follow  that  our  noble 
soliped  had  an  origin  less  remote  and  independent,  or  that  he  found 
it  necessary  and  practicable  to  concentrate  his  four  toes  into  one,  or 
succumb  to  the  altered  conditions  of  his  life  ? 


20  THE    HORSE    IN    MOTION. 

All  science,  in  whatever  department  of  knowledge,  is  retarded  much 
by  the  ignorance  and  zeal  of  the  multitude  who  follow  on  the  heels  of 
genius.  Medicine  has  its  mountebanks,  who  are  dragging  a  noble 
science  into  public  contempt ;  religion  has  its  harlequins,  and  natural 
science  its  buffoons,  who,  as  itinerant  lecturers,  perambulate  the  towns 
as  representatives  of  learning  they  do  not  possess,  and  put  forth  as 
proved  truth  the  wildest  speculations  of  enthusiasts,  and  call  them  sci- 
ence. It  is  very  common  to  hear  of  the  origin  of  man  from  the  ape, 
as  if  the  relation  were  a  scientific  truth,  when  in  fact  it  is  only  a  specu- 
lation ;  and  all  the  evidence  so  far  collected  from  fossil  remains  as  early 
as  the  tertiary  deposits  gives  no  confirmation  to  the  speculation.  As 
far  away  as  any  trace  of  the  prehistoric  man  has  been  found,  he  was  as 
perfectly  developed  as  he  is  to-day,  and  as  far  removed  from  the  ape. 

Darwin  is  not  responsible  for  what  is  known  as  Darwinism.  He 
is  a  model  for  a  naturalist,  collecting  facts  and  placing  them  in  their 
relation,  drawing  his  conclusions  cautiously,  and  candidly  admitting  the 
difficulty  when  a  fact  antagonizes  the  hypothesis  he  is  framing.  Not 
so  with  his  zealous  disciples,  who  rush  to  their  desired  conclusions 
over  his  facts,  as  the  fanatical  Christians  of  Alexandria  did  over  the 
last  vestal  altar  of  Greek  philosophy. 

Organic  life  is  the  result  either  of  chance  or  design ;  there  can  be 
no  middle  ground.*  If  the  latter,  the  question  of  how  it  was  brought 
about  will  never  be  solved  by  man,  nor  is  it  important  that  it  should  be. 
It  is  sufficient  that  a  Supreme  Intelligent  Will  is  the  author  and  sus- 
tainer  of  all,  —  a  beneficent  Spirit,  who 

*  Virchow,  who  will  be  recognized  as  one  of  the  leaders  in  the  new  departure  in  science  and 
the  cell  theory  of  development,  says  :  — 

"  This  much  is  evident.  If  I  do  not  choose  to  accept  a  theory  of  creation,  if  I  refuse  to  be- 
lieve that  there  was  a  special  Creator  who  took  the  clod  of  earth  and  breathed  into  it  the  breath 
of  life,  if  I  prefer  to  make  for  myself  a  verse  after  my  own  fashion,  then  I  must  make  it  in  the 
sense  of generalio  equiroca  (spontaneous  generation).  Tertiam  non  datur.  No  alternative  re- 
mains when  once  we  say,  '  I  do  not  accept  creation,  but  I  will  have  an  explanation.'  If  that  first 
thesis  is  laid  down,  you  must  go  on  to  the  second  thesis,  and  say,  '  Ergo,  I  assume  the  generalio 
equivocal  But  of  this  we  do  not  possess  any  actual  proof.  No  one  has  ever  seen  a  generatio 
equivoca  really  effected  ;  and  whoever  supposes  he  has  is  contradicted  by  the  naturalist,  and  not 
merely  by  the  theologian."  —  PROF.  VIKCHOW,  in  a  lecture  delivered  before  the  German  Asso- 
ciation of  Naturalists  and  Physicians  at  Munich,  1877. 


THE    HORSE    IN    MOTION.  _M 

"  \V;irms  in  the  sun,  refreshes  in  the  breeze, 
Glows  in  the  stars,  and  blossoms  in  the  trees, 
Lives  through  all  life,  extends  through  all  extent, 
Spreads  undivided,  operates  unspent  "; 

who  has  endowed  us  with  faculties  to  admire  the  beautiful,  the  good 
and  true,  to  know  why  so  many  things  arc  as  we  see  them,  but  none  to 
know  how* 

\  laving  given  some  of  the  reasons  for  his  belief  in  the  spiritual  ori- 
gin of  the  organic  world,  the  writer  claims  his  right,  whenever  he  has 
occasion  in  the  following  pages  to  do  so,  to  speak,  without  danger  of 
being  misunderstood,  of  design  or  contrivance  in  the  same  sense  that 
he  would  when  referring  to  similar  manifestations  of  design  in  a 
humanly  constructed  machine. 

In  a  theory  of  evolution,  as  the  expression  of  the  method  in  crea- 
tion, the  writer  has  little  doubt  that  the  thoughtful  mind  will  in 
due  time  rest  satisfied. 

*  "  The  consciousness  of  an  inscrutable  power,  manifested  to  us  through  all  phenomena,  has 
ln.i  n  growing  ever  clearer,  and  must  be  eventually  freed  from  its  imperfections.  The  certainty 
that,  on  the  one  hand,  such  a  power  exists,  while  on  the  other-hand  its  nature  transcends  intui- 
tion, and  is  beyond  imagination,  is  the  certainty  towards  which  intelligence  has  from  the  first 
been  progressing." — HERBERT  SPENCER,  First  Principles,  3d  edition,  p.  108. 

'•  When  the  remarkable  way  in  which  structure  and  functions  simultaneously  change  is  borne 
in  mind,  when  those  numerous  instances  in  which  nature  has  supplied  similar  wants  by  similar 
means  are  remembered,  when,  also,  all  the  wonderful  contrivances  of  orchids,  of  mimicry,  and 
the  strange  complexity  of  certain  instinctive  actions,  are  considered,  then  the  conviction  forces 
itself  on  many  minds  that  the  organic  world  is  the  expression  of  an  intelligence  of  some  kind. 
.  .  .  Organic  nature  then  speaks  clearly  to  many  minds  of  the  action  of  an  intelligence  resulting, 
on  the  whole  and  in  the  main,  in  order,  harmony,  and  beauty,  yet  of  an  intelligence  the  ways  of 
which  are  not  as  our  ways."  —  ST.  G.  MIVART,  F.  R.  S.,  in  Genesis  of  Species,  pp.  272,  273. 

"There  is  something  in  organic  progress  which  mere  natural  selection  among  spontaneous 
variations  will  not  account  for;  this  something  is  that  organizing  intelligence  which  guides  the 
action  of  the  inorganic  forces,  and  forms  structures  which  neither  natural  selection  nor  any 
other  unintelligent  agency  could  form." —  MURPHY,  Habit  and  Intelligence,  Vol.  I.  p.  348. 


CHAPTER   II. 

THE   HORSE  CONSIDERED  AS  A   MACHINE.  —  NECESSITY  or  UNDERSTANDING  ITS   CON- 
STRUCTION.—  GENERAL  PHYSIOLOGICAL  AND  ANATOMICAL  FACTS.  —  ARCHITECTURAL 

PRINCIPLES  INVOLVED  IN  THE  CONSTRUCTION  OF  THE  SKELETON OF  THE  JOINTS. 

-  THE  VERTEBRA.  —  THE  CARTILAGES  AND  LIGAMENTS.  —  THE  MUSCLES,  VOLUN- 
TARY AND  INVOLUNTARY.  —  GENERAL  FACTS,  ANATOMICAL,  PHYSIOLOGICAL,  AND 
MECHANICAL,  REGARDING  THE  MUSCLES.  —  ARTICULAR  LIGAMENTS.  —  TENDONS. — 
THE  LAW  OF  REPAIR  IN  MUSCLES  AND  TENDONS.  —  RELATION  OF  THE  FORM  OF 
ORGANS  TO  THEIR  FUNCTIONS.  —  UTILITY  MADE  TO  CONFORM  TO  BEAUTY  IN  THE 
FORM  OF  ORGANIZED  BEINGS. 

IT  is  proposed  to  present  as  concise  a  view  of  the  locomotive 
organs  of  the  horse  as  may  be  consistent  with  a  proper  knowledge  of 
the  parts,  and  the  functions  they  perform  in  progressive  motion. 

There  can  be  no  just  appreciation  of  the  qualities  of  a  complicated 
machine  without  a  comprehensive  understanding  of  its  construction, 
and  the  manner  in  which  each  of  its  parts  acts  to  produce  the  com- 
pound movement  for  which  it  was  designed.  So,  in  order  to  under- 
stand the  paces  of  the  horse,  we  must  understand  the  action  of  all 
the  parts  of  the  machinery  by  which  they  are  produced.  It  need 
not  be  said  that  it  is  very  complex,  and  has  never  been  understood, 
for  the  reason  that  the  motions  themselves  have  been  altogether  mis- 
interpreted. 

This  study  of  the  mechanism  of  the  horse  is  a  necessity  which  will 
become  apparent  to  any  one  who  undertakes  to  analyze  these  move- 
ments by  the  aid  of  any  manual  of  anatomy  yet  published.  The  dis- 
tinction of  muscles  into  adductors,  abductors,  extensors,  and  flexors 
gives  a  very  inadequate  idea,  and  sometimes  a  very  erroneous  one,  of 
the  action  of  the  muscles  to  which  those  terms  are  applied,  as  well  as 
to  their  general  agency  in  locomotion.  In  fact,  these  terms  are  used 
to  express  the  action  abstractly  with  reference  to  the  bones  to  which 


THE    HORSK    IN    MOTION.  33 

they  are  attached,  and  not  sufficient  attention  has  been  given  to  their 
action  in  correlation  to  the  others  with  which  they  are  coworkers. 
The  forces  employed  in  each  limb,  considered  alone,  are  very  complex. 
The  same  muscle  may  be  an  extensor  at  one  time  and  a  flexor  at  an- 
other in  the  same  stride,  as  we  shall  show  further  on. 

In  order  to  enable  the  reader  to  understand  the  muscles  and  their 
relations  without  too  great  a  tax  on  the  powers  of  abstraction,  the  ser- 
vices of  Mr.  William  Hahn.a  Diisseldorf  artist,  were  secured  to  delineate 
the  most  important  muscles  as  they  were  exposed  in  dissection  ;  but  no 
skill  can  do  justice  to  the  nacreous  tints  of  the  tendinous  envelopes 
of  the  deep  muscles.  With  all  the  aid  which  art  can  render,  the 
complicated  mechanism  of  the  horse  cannot  be  presented  by  written 
description  in  such  a  manner  as  to  dispense  with  a  little  close  attention. 
A  perfect  familiarity  with  the  subject,  so  as  to  enable  one  to  carry 
the  plan  of  the  whole  machine  in  the  mind,  can  only  be  attained  by  the 
aid  of  dissection.  A  knowledge  of  the  construction  of  the  machine 
is  imperative  upon  one  who  would  comprehend  its  action.  It  is 
as  necessary  as  for  an  engineer  to  understand  the  construction  of  his 
engine.  With  that  knowledge  one  can  understand  the  elements  of  a 
horse's  strength  and  speed,  analyze  his  movements,  and  appreciate  the 
source  of  the  danger  from  injury  in  great  trials  of  speed. 

Let  us  first  review  certain  physiological  and  general  anatomical 
facts,  well,  but  not  so  generally  known,  as  could  be  wished.  The  me- 
chanical parts  divide  themselves  into  two  classes,  the  active  and  pas- 
sive. The  passive  parts  are  the  bones  and  ligaments  ;  the  active  parts 
are  the  muscles  in  which  dwells  all  the  power. 

Of  the  bones  it  may  be  said,  in  general,  that  they  are  the  levers  on 
which  the  muscles  act,  and  by  means  of  which  their  power  is  made 
available  ;  their  form  depends  upon  the  uses  which  they  are  designed 
to  serve.  When  intended  for  bases  of  action,  they  are  thin,  angular, 
and  ribbed,  like  the  shoulder-blade,  or  scapula.  When  they  are  to  serve 
as  columns  of  support,  they  are  cylindrical ;  and  as  there  is  always 
the  utmost  economy  used  by  the  Creator  where  it  is  needed,  they  are 
made  hollow,  for  it  was  known,  as  long  ago  as  the  first  mammal  was 
made,  that  there  was  no  loss  of  strength  as  a  support  in  being  so  con- 


24  THE    HORSE    IN    MOTION. 

structed.  It  was  long  afterwards  discovered  by  man,  and  the  law  was 
learned  by  him,  that  the  lateral  strengths  of  two  cylindrical  bones  of 
equal  weight  and  length,  one  being  solid  and  the  other  hollow,  are  to 
each  other  as  their  diameters ;  and  the  spaces  in  the  shafts  of  these 
bones,  being  needless  for  the  purpose  of  support,  are  made  depositories 
of  fat  or  marrow  for  fuel,  —  literally,  coal-bunkers,  —  as  are  all  the  angu- 
lar spaces  not  needed  for  more  important  uses  throughout  the  body, 
by  means  of  which  heat  is  developed,  which  primarily  is  the  source  of 
all  motion  in  the  animate  as  well  as  the  inanimate  world. 

The  extremities  of  these  bony  columns  are  spread  out  to  give 
broader  articulating  surfaces ;  at  the  same  time  the  single  hollow  of 
the  shaft  is  divided  into  innumerable  small  ones,  so  that  greater 
strength  is  attained  to  resist  the  wrenching  force  to  which  they  are 
liable,  without  increase  of  weight ;  roughened  ridges,  spines,  and  pro- 
tuberances *  are  formed  to  give  greater  surface  for  the  attachment  of 
muscles.  For  the  purpose  of  still  further  increasing  the  surface  for 
attachment  of  muscles,  supplemental  bones  are  added,  as  in  the  splint 
bones,  —  or,  as  they  are  called  by  anatomists,  the  little  metacarpels,  — 
which  not  only  serve  to  widen  the  articulating  surface,  but,  by  a  strong 
ligamentous  membrane  that  connects  them  with  the  main  pillar,  give 
the  necessary  space  for  attachment  of  important  muscles,  and  where 
the  distance  from  the  centre  of  motion  renders  the  reduction  of  weight 
very  important,  as  the  rapidity  with  which  these  extremities  move 
increases  greatly  with  the  distance  from  the  centre  of  motion.  The 
bones  are  composed  of  animal  and  earthy  matter,  in  the  proportion 
of  about  one  of  the  former  to  two  of  the  latter.  If  the  proportion 
of  the  former  is  increased,  they  will  bend  under  the  force  applied  to 

*  Atheists  maintain  that  function  makes  the  organ  ;  but  how  can  we  conceive  of  function 
without  previous  conception  of  the  organ  ?  What  conception  can  be  formed  of  sight  without 
the  existence  of  the  eye  ?  It  is  held  by  them  that  the  roughened  ridges  and  protuberances  of 
bone  are  developed  by  traction  of  muscles  upon  the  bony  surfaces.  If  this  is  so,  why  is  it  that 
the  surface  of  the  bone  above  the  acetabulum  which  receives  the  insertion  of  the  recttts  fctno- 
ris  is  smooth  ?  It  certainly  is  not  because  there  is  want  of  traction  on  the  part  of  that  muscle. 
On  the  other  hand,  the  tensor  va°ince  femoris  and  the  superficial  glutens,  whose  insertions  are 
low  down  on  the  femur  for  the  necessary  leverage,  must  find  room  between  other  muscles,  and 
a  rough  protuberance  is  formed  to  give  the  most  surface  for  attachment  in  the  least  space. 


THK    IIORSK    IN     MOTION.  25 

them  ;  and  if  the  proportion  of  the  latter  is  increased,  they  are  liable  to 
break.  Variation  from  the  normal  proportions  is  the  result  of  disease, 
and  is  more  common  in  the  human  family  than  among  quadrupeds. 

The  bones  are  covered  with  a  compact,  inelastic  fibrous  membrane, 
the  periosteum,  which  adheres  so  closely  to  their  surfaces  that  consider- 
able force  is  required  to  detach  it.  This  membrane  serves  not  only  to 
nourish  the  bones  through  its  blood-vessels,  or  vascular  system,  but  to 
strengthen  them  and  increase  their  elasticity.  The  Californian  Indian 
adopts  the  same  method,  for  the  same  purpose,  in  the  construction  of 
his  bow.  In  studying  the  architecture  of  the  skeleton,  as  a  whole,  it 
will  be  found  that  no  element  of  strength  is  wanting,  or  principle  of 
mechanics  violated,  in  its  structure.  The  bones  are  arched  or  bent 
when  such  forms  give  greater  strength.  They  are  connected  to  each 
other  by  a  strong  tissue,  so  flexible  as  to  allow  of  the  greatest  free- 
dom of  motion,  but  inextensible,  and,  under  all  ordinary  use,  too  strong 
to  be  broken  or  detached  from  the  bony  levers  whose  motion  it  is 
designed  to  limit.  It  is,  however,  sometimes  torn,  either  completely 
or  partially,  in  dislocations  or  sprains ;  and  the  slightest  injury  to  this 
tissue  is  a  serious  accident  to  an  animal  whose  value  depends  on  the 
soundness  of  his  locomotive  organs. 

The  extremities  of  bones  which  move  upon  each  other,  as  at  the 
joints  or  articular  surfaces,  are  covered  with  a  peculiar  formation 
known  as  cartilage.  It  is  insensible  in  a  state  of  health,  and  very 
elastic  to  pressure ;  thickest  where  most  exposed  to  concussion,  and 
covered  with  a  membrane  which  secretes  a  glairy  fluid  adapted  to 
lubricate  the  opposing  surfaces  and  reduce  friction.  These  joints  are 
all  closed  to  the  admission  of  atmospheric  air  and  all  foreign  sub- 
stances, for  their  admission  would  soon  cause  serious  injury. 

The  joints  are  divided  by  anatomists  into  several  classes,  according 
to  their  mechanical  construction.  Some  are  simple  hinges,  admit- 
ting of  motion  in  one  direction  only,  as  those  of  the  lower  parts  of 
the  extremities.  The  heads  of  all  the  four  columns  of  support  are 
provided  with  a  kind  of  joint  known  to  mechanics  as  the  ball  and 
socket.  This  form  admits  of  the  greatest  freedom  of  motion  in  every 
direction ;  but  the  motion  is  limited  in  extent  by  capsular  ligaments 


26  THE    HORSE    IN    MOTION. 

which  surround  the  joints  as  a  continuous  collar,  whose  borders  are 
attached  to  each  of  the  bones  so  far  from  the  opposing  surfaces  as  not 
to  intervene,  and  yet  not  so  far  that  they  may  not  limit  the  motion  to 
its  needs.  These  capsular  ligaments  serve  another  useful  purpose. 
Being  air-tight,  when  the  limb  is  off  the  ground  it  is  supported  in  its 
place  by  the  pressure  of  the  atmosphere,  —  estimated  by  Borelli  to  be 
equal,  in  the  hip  joint  of  a  man,  to  a  lifting  force  of  twenty-six  pounds. 
The  force  thus  gained  is  set  free  to  be  employed  in  locomotion.  Each 
joint  constitutes  by  itself  an  interesting  subject  for  study,  as  they  all 
differ  in  some  important  particular,  according  to  their  uses.  The 
construction  of  the  hock  joint  is  quite  unique,  and  has  no  analogue 
in  man ;  and  that  of  the  hock  of  the  ox  is  quite  different  from  that  of 
the  horse.  The  interlocking  grooves  are  oblique,  so  that  when  the 
posterior  extremity  is  brought  forward  to  pass  its  fellow,  fixed  upon 
the  ground,  it  is  carried  obliquely  outward,  independently  of  volition  ; 
and  when  all  danger  of  interference  is  passed,  and  the  limb  is  again 
extended  to  reach  the  ground,  the  foot  is  carried  obliquely  inwards,  to 
resume  its  place  under  the  centre  of  gravity.  This  will  be  referred  to 
more  fully  when  considering  the  action  of  the  posterior  extremity. 
The  construction  of  the  joints  at  large  would  serve  as  a  subject  for  a 
monograph  of  great  interest;  but  to  be  fully  understood  it  must  be 
studied  ensis  in  manu. 

A  detailed  description  of  the  bones  will  not  be  attempted.  They 
are  proverbially  a  dry  subject ;  but  for  the  convenience  of  those 
who  require  it,  a  reference  plate  is  presented,  lithographed  from  a 
photograph;  and  it  is  hoped  that  it  will,  through  the  eye,  give  the 
necessary  information  to  enable  the  reader  to  understand  the  mechan- 
ical movements  without  the  study  which  abstract  description  would 
require.  But  the  vertebra,  or  spinal  column,  as  the  keel  or  bed-plate 
connecting  the  various  parts  of  the  machinery,  requires  further 
attention. 

The  term  "spinal  column,"  as  applied  to  the  skeleton  of  quadrupeds, 
is  a  misnomer,  derived,  like  most  anatomical  names  in  comparative 
anatomy,  from  its  analogue  in  man.  The  spine  being  horizontal 
in  quadrupeds,  and  not  vertical,  as  in  man,  the  term  "  column " 


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THE   HORSE    IN    MOTION.  27 

is  inapplicable  to  them.  The  word  "  spine "  is  also  objectionable, 
as  it  is  derived  from  the  processes  which  superficially  mark  its 
course.  There  seems  to  be  no  objection  to  the  term  "  vertebra,"  as 
a  collective  noun  applied  to  the  whole  or  any  number  of  its  parts.  As 
it  is  the  keel  and  connection  of  the  various  parts  of  the  animated 
engine,  so  it  is  the  term  from  which  has  been  derived  the  name  for  the 
whole  divi>ion  of  animals  to  which  quadrupeds  belong,  —  Vertebrates. 

The  vertebra  of  the  horse  is  divided  into  five  groups,  differing  ma- 
terially in  their  mechanical,  even  more  than  in  their  physiological  rela- 
tions. These  groups  are  the  Cervical,  the  Dorsal,  the  Lumbar,  the 
Sacral,  and,  lastly,  the  Caudal.  The  cervical  vertebras  have  an  im- 
portant relation  to  locomotion,  second  to  no  other  division.  They  are 
provided  with  spines  along  the  median  plane,  as  are  all  the  vertebrae, 
and  transverse  projections  or  processes,  which  afford  attachments  to 
ligaments  to  maintain  their  relative  positions ;  and  with  important 
muscles,  as  will  be  shown  in  a  subsequent  chapter.  There  is  great 
freedom  of  motion  of  these  bones  upon  each  other,  in  comparison 
with  those  of  the  next  two  divisions,  especially  at  the  articulation  with 
the  head  and  the  first  vertebra  of  the  trunk.  This  last  is  a  ball  and 
socket  joint  of  a  peculiar  construction,  to  enable  the  animal  to  reach 
the  ground,  as  in  grazing  and  drinking. 

The  second  group  is  the  dorsal,  and  it  consists  of  those  vertebras 
that  are  articulated  with  the  ribs.  Like  the  cervical,  these  are  pro- 
vided with  transverse  processes,  which  serve  not  only  for  muscular 
and  ligamentous  attachments,  but  as  braces  to  the  ribs.  The  spinous 
processes  are  longer  than  those  of  any  of  the  other  vertebras,  especially 
along  the  withers,  where  the  suspending  muscles  of  the  anterior  extrem- 
ity originate.  It  will  be  apparent  to  the  most  superficial  observer  that 
the  motion,  either  lateral  or  vertical,  of  the  dorsal  vertebrae  upon  each 
other  is  very  circumscribed,  being  limited  in  a  vertical  direction  by  the 
long  spinous  processes  and  their  intermediate  inelastic  ligaments,  and 
in  a  lateral  direction  by  the  transverse  processes  and  their  articulating 
ribs.  The  next  division  is  that  of  the  lumbar  region,  or  the  vertebras 
of  the  loin,  with  which  there  are  no  connecting  ribs.  As  the  former 
group  was  more  intimately  related  to  the  thorax,  so  those  of  the  lum- 


28  THE    HORSE    IN    MOTION. 

bar  are  in  the  same  relation  with  the  abdomen.  Their  broad  and 
long  transverse  processes  afford  a  protecting  roof  to  the  abdominal 
viscera,  and  give  attachment  to  important  muscles  of  locomotion  on 
the  under  surface.  There  is  very  little  movement  of  these  bones 
upon  each  other,  even  less  than  in  the  dorsal  series,  —  so  little  that 
bony  union  takes  place  between  them  in  old  age ;  and  the  elastic 
cartilages  that,  at  an  earlier  period  of  life,  were  interposed  between 
each  of  the  vertebra  become  degenerated  into  bony  matter,  and  that 
condition  obtains  technically  known  as  ankylosis. 

The  next  series,  and  fourth  in  order,  is  the  Sacral.  Though  in 
the  embryotic  stage  the  sacrum  is  developed  from  several  centres  as  dis- 
tinct vertebra,  yet  before  birth  they  are  united  into  one  broad  triangular 
bone,  which,  uniting  with  the  iliac  bones  on  each  side,  and  the  pubic 
bones  in  front,  forms  the  ring  known  as  the  pelvis.  It  is  in  the  lower 
or  pubic  portion  of  this  pelvis  that  the  cuplike  cavities  are  formed 
into  which  the  heads  of  the  hip  bones  are  lodged,  and  where  the  force 
of  the  levers  of  the  posterior  extremities  is  applied.  The  difficulty 
in  locomotion  that  would  be  experienced  from  the  want  of  flexibility 
of  the  spine,  especially  in  old  age,  is  obviated  by  the  freedom  of 
motion  that  is  secured  in  the  articulation  of  the  last  of  the  dorsal 
vertebra  with  the  sacrum.  This  is  what  is  known  as  the  "coupling," 
as  it  unites  the  two  distinct  systems  of  locomotive  organs,  the  anterior 
and  posterior  extremities.  In  the  skeleton  the  connection  seems  very 
slight;  but  the  ligamentous  connections  are  very  strong,  and  the  long 
muscle  of  the  back  (longissimus  dorsi  or  ilio  spinalis),  reaching  out 
from  its  spinal  attachments,  lays  hold  of  the  hip  bone  (crest  of  the 
ilium)  on  each  side  as  far  as  possible  from  the  centre  of  motion  at  the 
coupling,  the  more  effectually  to  limit  the  flexion  at  that  point. 

The  last  group  of  vertebral  bones  is  known  to  anatomists  as  the 
coccyx,  from  its  resemblance  in  man  to  the  beak  of  the  cuckoo;  but  as 
the  resemblance  totally  fails  in  the  Mammalia  and  all  other  vertebrates, 
we  shall  call  them  by  the  more  general  name  of  Caudal  bones.  They 
have  no  function  in  locomotion ;  but  "  thereby  hangeth  a  tale." 

Between  all  the  vertebral  bones  is  interposed  a  layer  of  clastic  carti- 
lage, of  the  same  nature  as  that  which  covers  the  opposing  surfaces 


THE    HORSE    IX    MOTION.  29 

of  the  joints  in  the  extremities.  These  cartilages  by  their  elasticity 
admit  of  slight  flexion  of  the  vertebra,  and  they  also  deaden  the  force 
of  the  shock  transmitted  from  the  powerful  impulses  of  the  posterior 
limbs.  As  has  been  already  stated,  the  flexion  is  limited  by  the  liga- 
ments which  bind  them  to  each  other.  This  restriction  of  motion  is 
necessary  for  the  protection  of  the  vital  organs  of  the  thorax  and 
abdomen,  as  well  as  the  great  nerve  trunk  transmitted  through  a 
continuous  canal  above  the  bodies  of  the  vertebra,  and  which  is  dis- 
tributed thence  to  all  parts  of  the  body. 

While  the  three  central  divisions  of  the  vertebra  may  be  curved 
slightly,  they  cannot  be  shortened,  even  temporarily,  as  may  be  readily 

:i ;  and  the  apparent  shortening  that  takes  place  when  the  animal's 
limbs  are  gathered  under  him  is  an  illusion.  The  elasticity  of  the 
cartilages  and  ligaments  is  greatest  in  the  young ;  as  age  advances, 
these  tissues  become  stronger  and  less  flexible,  and  resist  the  move- 
ments of  the  joints;  they  are  said  to  become  "stiff."  Hence  the 
importance  of  early  training  to  give  greater  sweep  and  freedom  of 
motion.  This  physiological  principle  is  made  the  basis  of  gymnastic 
training  by  acrobats,  being  commenced  at  a  very  early  age;  and  the 
same  is  not  lost  sight  of  in  the  exercises  of  colts. 

In  contemplating  the  passive  parts  of  the  animated  machine  ab- 
stractly, we  see  the  results  of  organic  life ;  they  are  without  sensi- 
bility or  power  of  spontaneous  motion ;  we  are  familiar  with  the 
mechanical  principles  involved  in  their  action,  and  are  impressed  by 
the  perfect  adaptation  of  means  to  ends ;  we  look  upon  them  as  we 
look  upon  the  piston,  connecting-rod,  and  crank  of  a  steam-engine  : 
but  upon  the  muscles  we  look  with  far  different  thoughts ;  their  action 
has  no  similitude  in  the  inanimate  world. 

The  general  appearance  of  muscle  is  too  familiar  to  every  one  to 
need  description  ;  its  special  vital  property  is  contractility.  The  mus- 
cles are  both  voluntary  and  involuntary,  but  it  is  only  the  former  that 
are  concerned  in  locomotion. 

If  we  remove  a  fragment  of  muscle  from  an  animal  recently  killed 
and  examine  it  closely,  we  shall  find  it  to  be  made  up  of  longitudinal 
fibres  of  a  red  color  bound  together  by  gray  fibres  of  a  different  tissue. 


30  THE   HORSE   IN   MOTION. 

If  we  lay  this  flake  of  muscle  upon  a  plate  and  scrape  it  gently  in  the 
direction  of  its  fibres  with  a  dull  knife,  we  shall  find  upon  the  edge  of 
the  knife  a  red  pulp  without  apparent  fibre  or  tenacity,  and  there  will 
be  left  behind  a  bundle  of  strong  cellular  tissue.  It  is  to  the  former 
that  the  tractile  property  belongs ;  the  latter  has  no  more  active  power 
than  other  cellular  tissue ;  yet  this  pulpy  bundle  of  fibres,  as  muscle, 
contracts  under  the  stimulus  of  the  will  with  almost  inconceivable 
power.  Borelli  estimated  that  the  force  exerted  by  the  deltoid  muscle 
of  man  in  supporting  a  weight  held  horizontally  in  the  hand  was  two 
hundred  and  nine  times  greater  than  the  weight.  Therefore  a  weight 
of  sixty  pounds  held  horizontally  requires  an  expenditure  of  contractile 
force  of  the  extensor  muscles  at  the  shoulder  of  more  than  six  tons. 
He  demonstrated  that  the  force  of  the  extensors  employed  by  a  porter 
in  carrying  a  weight  of  one  hundred  and  fifty  pounds  upon  the  shoul- 
der exceeds  three  tons.*  It  follows  that  this  enormous  power  is 
exerted  on  the  extensors  of  each  leg  alternately. 

The  natural  stimulant  to  the  muscle  is  the  will  transmitted  through 
the  nerves;  but  the  will  is  not  necessary  to  muscular  contraction,  as  it 
has  no  influence  on  the  muscles  of  animal  life  or  the  vegetative  func- 
tions of  animals,  and  any  of  the  voluntary  muscles  may  be  cut  off  from 
communication  with  the  brain  by  severing  its  nervous  connection  ;  yet 
contraction  may  be  excited  in  the  muscle  so  cut  off,  and  this  may  be 
continued  indefinitely  by  further  division  to  a  microscopic  degree  ;  still 
the  fibres  will  be  observed  to  contract  upon  the  slightest  touch,  so 
closely  are  the  nervous  fibres  interwoven  with  those  of  the  muscle. 

Electricity  when  passed  through  the  muscle  in  a  broken  current  is 
a  strong  excitant  to  muscular  contraction,  overmastering  the  will,  and 
will  even  cause  contraction  after  life  has  left  it ;  but  if  the  current  is 
continuous,  it  has  no  such  power. 

The  muscular  fibres  are  paralyzed  by  certain  poisons,  and  stimulated 
to  violent  contraction  by  others  ;  and  in  disease,  as  tetanus,  they  may 
be  so  violently  stimulated  as  to  be  torn  asunder.  This  subject,  though 
very  interesting,  is  leading  away  from  the  special  inquiry  to  which  we 

*  Cyclopaedia  of  Anatomy  and  Physiology,  art.  "  Animal  Motion." 


THE    HORSE    IN    MOTION.  31 

are  limited.  The  muscles  are  subject  to  fatigue,  and  are  unable  to 
respond  indefinitely  with  equal  force  to  the  will. 

Muscular  fibre  has  other  properties  to  be  considered  in  relation  to 
motion.  Its  contractility  is  limited  to  one  fourth*  or  one  third  t  of  the 
length  of  the  fibre,  and  with  a  power  proportioned  to  the  area  of  the 
transverse  section  of  the  muscle.  It  will  be  found  that  the  relation  of 
length  to  thickness  is  as  action  to  power. 

Deep-seated  muscles  are  often  attached  to  the  bones  upon  which 
they  act  directly ;  but  as  there  is  insufficient  space  on  the  surface  of  the 
bones  for  all  that  depend  upon  them,  the  extremities  of  the  muscles  are 
often  changed  into  tendon,  —  a  substance  altogether  different  in  its  me- 
chanical properties,  being  compact,  very  flexible,  and  incapable  of  elon- 
gation, in  order  that  it  may  not  give  away  the  contraction  effected  by 
the  muscular  tissue.  By  means  of  this  tendinous  tissue  the  power  of 
the  muscle  is  transmitted  when  necessary  to  a  considerable  distance,  or 
its  direction  may  be  changed  by  the  tendon  passing  through  a  sheath 
or  groove,  as  a  pulley,  over  an  angle.  In  a  humanly  contrived  machine 
it  has  been  found  necessary,  when  the  direction  of  the  action  of  the 
power  requires  to  be  changed,  to  use  a  friction  roller  or  pulley ;  but 
nature  has  done  better,  and  contrived  a  way  to  avoid  friction  and  wear 
that  human  ingenuity  cannot  hope  to  rival.  By  these  means  the  power 
generated  in  the  heavy  muscles  is  exerted  at  the  extremities  of  the 
limbs  where  all  needless  weight  requires  such  great  expenditure  of 
power  to  give  it  the  needful  velocity.  The  power  which  is  conserved 
in  the  body  as  momentum  would  be  lost  in  the  extremities,  for  the 
motion  of  the  limbs  is  arrested  at  every  stride.  $  The  attachment 
of  these  tendons  to  the  bones  and  the  periosteum  enveloping  them  is 
so  great  that  detachment  by  natural  means  is  not  mentioned  in 
works  on  farriery  as  among  the  possible  accidents  to  which  the  horse 
is  liable. 

*  Bishop. 

t  Bowman,  Cyc.  Anat.  and  Phys. 

J  If  a  weight  of  25  Ibs.,  sustained  by  the  hand  of  an  arm  extended  horizontally,  requires  the 
expenditure  of  an  energy  equal  to  2oq  times  that  weight,  or  5,225  Ibs.,  what  amount  of  muscular 
force  is  expended  by  the  muscles  of  one  of  the  extremities  of  a  horse  to  move  a  4-ounce  shoe  on 
his  foot  when  he  is  trotting  at  the  rate  of  a  mile  in  2  min.  20  sec.? 


32  THE   HORSE   IN    MOTION. 

During  the  life  of  the  animal  the  tenacity  of  the  muscle  is  greater 
than  that  of  its  tendon,  but  when  vitality  no  longer  animates  it  it  may 
be  easily  torn. 

While  the  articular  ligaments  are  subject  to  extension  and  elonga- 
tion by  early  use  and  frequent  tension,  so  that  greater  freedom  of 
motion  than,  is  normal  is  acquired,  it  is  otherwise  with  the  muscular 
tissue  and  its  tendons.  By  exercise  within  certain  limits,  at  regular 
intervals,  and  with  proper  nutrition,  the  thickness  and  power  of  the 
muscles  may  be  increased,  and  by  neglect  of  these  conditions  they  will 
become  thin  and  pale,  while  contraction  will  be  feeble  and  not  well 
sustained  ;  but  they  will  not  become  elongated  under  whatever  violent 
and  long-sustained  exercise ;  they  may  increase  in  thickness,  but  not 
in  length.  But  for  this  exception  to  the  rule  the  whole  plan  on  which 
animal  mechanics  was  founded  would  have  fallen  to  the  ground  with 
the  animal  himself.  Were  the  muscles  to  become  lengthened  by  use 
without  corresponding  increase  in  length  of  levers,  the  tension  neces- 
sary to  prompt  action  would  be  lost,  and  the  effect  would  be  similar 
to  that  upon  the  tiller  ropes  of  a  ship  were  they  to  become  relaxed. 
What  would  be  the  effect  upon  the  length  of  the  bones  in  the  period 
of  time  contemplated  by  some  it  is  useless  to  inquire,  but  we  know 
that  the  increase  of  muscular  power  by  increase  in  the  bulk  of  the 
muscle  takes  place  in  a  short  period,  and  in  the  lifetime  of  the  indi- 
vidual. But  while  the  muscles  and  their  levers  will  retain  their  nor- 
mal relation  of  length  during  life  in  a  healthy  subject,  that  balance  is 
sometimes  lost  as  the  result  of  injury.  A  child  has  been  run  over  by 
a  wagon ;  the  wheel  has  passed  over  the  muscles  of  the  calf  so  as  to 
disorganize  the  muscular  tissue;  in  due  time  the  injured  part  is  re- 
stored to  health,  but  the  muscle  does  not  develop  fully ;  it  is  shortened, 
and  a  form  of  club  foot  is  the  result,  in  which  the  person  cannot,  while 
walking,  reach  the  ground  with  the  heel.  The  child  has  grown  to 
manhood,  but  no  amount  of  use  and  no  length  of  time  will  elongate 
the  muscle.  Nature  cannot  elongate  that  muscle  without  anarchy. 
The  Creator  works  by  law,  and  to  claim  an  exception  is  virtually  an 
admission  that  we  do  not  understand  the  law.  But  what  He  cannot 
do  without  anarchy  his  creature  can ;  he  slips  a  tenotomy  knife 


THE    HORSE    IN    MOTION.  33 

beneath  the  tendon,  severs  it  with  scarcely  a  visible  external  wound, 
the  muscular  fibres  retract  the  severed  ends,  and  that  ever-present, 
inscrutable  power  fills  in  the  space  left  by  the  parted  extremities  of  the 
tendon  with  new  tendon,  the  organ  is  restored  to  proper  length,  and 
the  deformity  is  removed.  If,  on  the  other  hand,  one  of  the  bony  col- 
umns of  support  be  broken,  —  for  example,  the  thigh,  —  the  creative 
power  called  nature  soon  sets  at  work  to  repair  the  damage.  A  seques- 
trum, or  casing,  is  formed  around  the  broken  extremities,  consisting  of 
inelastic  bony  matter,  to  fix  them  in  their  position  as  a  temporary  expe- 
dient, while  the  slower  processes  of  the  more  thorough  organization  of 
perfect  bone  is  effected,  and  the  fracture  is  repaired,  after  which  the 
sequestrum  is  absorbed  and  carried  off  through  the  circulation.  While 
this  change  has  been  taking  place  in  the  bone,  it  would,  without  surgi- 
cal interference,  in  most  cases  be  shortened  by  overlapping  through  the 
contraction  of  the  muscles  on  all  sides  of  it.  The  consequence  would 
be  that  the  same  disaster  would  be  encountered  as  in  the  last  case, 
where  the  muscles  were  supposed  to  be  elongated  from  use  ;  but  another 
law  is  observed.  The  muscle  that  could  not  elongate  will  shorten,  and 
the  proportion  between  the  length  of  the  lever  and  the  muscles  which 
act  upon  it  is  restored. 

It  is  said  by  Professor  Marey  that  "  the  comparison  between  ordinary 
machines  and  animated  motive  powers  will  not  have  been  made  in  vain 
if  it  has  shown  that  strict  relations  exist  between  the  form  of  the  organs 
and  the  character  of  their  functions ;  that  this  correspondence  is  regu- 
lated by  the  ordinary  laws  of  mechanics ;  so  that  when  we  see  the  mus- 
cular and  bony  structure  of  an  animal  we  may  deduce  from  their  form 
all  the  characters  and  functions  they  possess."  This  statement,  which 
/;/  the  main  appears  to  be  true,  requires  qualification.  The  form  of 
many  muscles  is  made  to  conform  to  the  situation  and  relation  of  sur- 
rounding organs.  Nature,  while  prodigal  where  she  can  afford  to  be, 
i.^  economical  where  there  is  need  of  it.  This  is  shown  in  numerous 
ways,  and  especially  in  the  form  and  arrangement  of  muscles. 

Beauty  of  form  is  never  lost  sight  of  in  the  construction  of  the 
horse;  and  even  great  sacrifices  of  mechanical  power  are  made  to 
maintain  graceful  lines,  and  that  general  contour  of  form  that  gave 

s 


34  THE   HORSE    IN    MOTION. 

to  him  his  matchless  beauty, —  beauty  so  great  that  to  the  eye  of  a 
superficial  observer  it  is  difficult  to  decide  whether  it  is  subordinate  to 
strength  or  conversely.  Both  are  developed  in  a  perfect  horse  to  such 
a  degree  that  he  has  been  a  favorite  theme  of  poets  and  painters  since 
aesthetic  culture  has  had  a  place  in  the  history  of  our  race. 

Numerous  instances  might  be  referred  to  where  use  has  been  sacri- 
ficed to  economy  of  space  and  to  beauty;  but  they  cannot  fail  to  occur 
to  the  mind  of  the  anatomist ;  and  it  is  premature  to  introduce  them  in 
this  place  for  the  general  reader. 


CHAPTER    III. 

SPECIAL  ANATOMY.  —  NECESSITY  OF  TECHNICAL  TERMS. — THE   ILIO  SPINALIS. —  DEFI- 
NITION  OF  TERMS   — PSOAS   MAGNUS.  —  I  I.I  ACL'S.  —  TENSOR    VAGIN*    FEMORIS. —  SAR- 

TORIUS.  —  PECTINEUS,  SMALL  ADDUCTOR,  ETC.  —  GREAT  GLUTEUS.  —  DEEP  GLUTEUS. 
—  LONG  VASTUS.  —  SEMI-TENDINOSUS.  —  SEMI-MEMIIKANOSUS.  —  GREAT  ADDUCTOR.  — 
GRACILIS.  —  THE  ADDUCTION  AND  ABDUCTION  OK  MUSCLES.  —  TRICEPS  FEMORIS. — 
GASTROCNEMII. —  AUTOMATIC  ACTION  IN  THE  .HIND  LEG.  —  THE  PERFORANS  AND 
PERFOKATVS  MUSCLES  AND  THEIR  TENDONS.  —  SUSPENSORY  LIGAMENT.  —  DIFFICUL- 
TIES IN  THE  U'AY  OE  DETERMINING  THE  AMOUNT  OF  WORK  DONE  BY  MUSCLES. — 

ELONGATION  AND  CONTRACTION  OF  THE  LIMBS.  —  INTERFERENCE  AND  STIFLE  ACTION. 
—  THF.  ACTION  OF  THE  HOCK  JOINT  TO  PREVENT  INTERFERENCE.  —  THE  ORDER  OF 
ACTION  IN  THE  VARIOUS  MUSCLES  OF  THE  POSTERIOR  EXTREMITY  IN  LOCOMOTION. 

FROM  the  general  observations  of  the  last  chapter  we  will  proceed 
to  a  consideration  of  the  special  anatomy,  and  analyze  the  locomo- 
tive organs  of  the  horse  ;  without  this  preparatory  study  it  will  be 
impossible  for  any  one  to  analyze  its  movements. 

Those  who  have  studied  and  suppose  they  understand  this  action 
must  study  again.  Let  no  one  be  turned  from  this  subject  by  tech- 
nical terms ;  they  are  indispensable  in  order  to  make  one's  self  under- 
stood by  those  who  have  already  made  a  study  of  anatomy,  as  well 
as  to  those  who  would  follow  the  movements  by  which  the  various 
paces  are  performed,  and  speak  of  a  horse  in  more  intelligible  terms 
than  the  slang  of  jockeys  and  the  stables.  I  think  I  am  warranted 
in  the  belief  that  we  are  on  a  new  era  in  the  history  of  our  old 
friend  and  fellow-traveller;  the  increasing  interest  that  is  felt  in 
America  as  well  as  Europe,  and  the  impulse  that  is  sure  to  be  com- 
municated by  the  wonderful  revelations  of  the  camera,  justify  me 
in  that  opinion.  I  shall  not  follow  the  usual  order  of  descriptive 
anatomists. 

It  has  already  been  stated  that  it  is  not  the  purpose  of  this  essay 
to  teach  anatomy  any  further  than  is  necessary  to  demonstrate  the 


36  THE    HORSE    IN    MOTION. 

mechanism  of  the  locomotive  organs,  and  the  manner  in  which  the 
muscles  act  upon  their  bony  levers  to  produce  the  movements  in 
progressive  motion. 

The  long  muscle  of  the  back  holds  the  same  relation  to  the  loco- 
motive muscles  that  the  vertebra  does  to  the  bones ;  it  is  a  very  com- 
plex muscle  or  system  of  muscles ;  it  is  called  by  Chauveau  the  ilio 
spinalis,  so  named  from  its  attachments.  It  fills  the  angular  space 
on  each  side  of  the  spinous  processes,  giving  roundness  to  the  back. 
It  is  very  broad  and  thick  over  the  loins,  and  is  attached  to  the 
whole  anterior  border  of  the  ilium  and  strongly  to  its  crest,  or  the 
hip  bone,  as  seen  in  Plate  III.,  q;  it  is  attached  anteriorly  to  all 
the  spines  of  the  vertebra,  as  far  as  the  neck,  and  a  strong  mem- 
brane, tendon-like  in  its  construction,  that  is  firmly  fastened  to  the 
same  bones.  This  tendinous  membrane,  called  aponeurosis,  has 
not  been  mentioned  thus  far,  but  it  is  tissue  very  important  in 
its  relation  to  the  muscles;  it  differs  from  fascia  in  several  respects, 
but  specially  in  thickness  and  strength.  It  covers  nearly  all  the 
superficial  muscles,  and  its  strength  is  so  great  that  the  muscular 
fibres  are  attached  to  its  inner  face  as  to  a  bone,  and  it  serves  them 
often  the  same  purpose  as  fixed  attachments.* 

If  one  takes  an  elevated  seat  with  the  driver  on  a  coach,  and 
looks  down  upon  the  wheel  horse  nearest  him,  he  can  see  the  action 
of  this  muscle,  and  to  the  best  advantage  if  the  horse  is  trotting. 
It  will  be  noticed  that  the  spine  is  flexed  in  a  serpentine  manner 
as  the  diagonal  legs  move  alternately.  This  movement  is  caused 
by  the  impulses  given  to  the  pelvis  by  the  heads  of  the  femurs 
alternately,  which  would  seriously  strain  the  articulation  of  the  pel- 
vis with  the  lumbar  vertebra  called  the  coupling,  but  for  the  action 
of  the  ilio  spinalis,  which  contracts  simultaneously  with  the  impulse 
communicated  to  the  opposite  side  of  the  pelvis,  acting  as  a  brace 
checking  the  wrenching  violence  of  the  action  and  preventing 
injury  to  the  coupling.  This  is  the  function  of  the  iliac  wings,  as 

*  A  familiar  example  may  be  seen  in  a  porter-house  steak  of  beef.  The  part  known  as 
the  tenderloin  is  a  section  of  the  psoas ;  that  above  is  a  section  of  the  ilio  spinalis  over- 
laid by  its  aponeurosis. 


PERFICIAL    LOCOMOTIVE    M.U3CLES     EXPOSED 


THK    HORSI-:    IN    MOTION.  37 

referred  to  in  Plate  V.,  a,  a,  a.  The  great  mass  of  the  muscle 
which  fills  the  angular  spaces  on  each  side  the  spines  is  called 
into  action  in  rearing,  or  supporting,  the  anterior  half  of  the  body 
when  not  supported  by  one  of  the  fore  legs.  The  greater  part 
of  the  ilio  spinalis  is  concealed  in  the  plate  by  the  great  glu- 
tcus,  f,  f,  c.  The  centres  of  motion  between  the  vertebra  are  in  the 
bodies  of  those  bones  which  are  most  distant  from  the  spines,  and 
which  form  the  rounded  ridge  of  the  backbone  as  seen  in  the  great 
cavity  of  the  trunk.  In  man  they  constitute  the  supporting  column. 
The  ilio  spinalis  muscle  lies  wholly  above  this  axis,  and  its  action 
abstractly  would  curve  it  downward ;  it  can  have  no  influence,  there- 
fore, in  aiding  to  support  a  back  load.  The  mechanical  action  of 
this  long  and  powerful  muscle  is  therefore,  first,  when  they  both  act 
in  unison  to  support  the  anterior  half  of  the  body  while  the  pelvis 
is  fixed  by  other  muscles;  and  in  the  second  place,  when  they  act 
alternately,  to  counteract  the  wrenching  effect  of  the  propulsion  of 
the  heads  of  the  thigh  bones. 

Before  we  proceed  any  further  with  the  consideration  of  the  mus- 
cles of  locomotion,  we  must  agree  upon  the  signification  of  terms 
necessary  to  be  employed. 

The  words  "  flexor  "  and  "  extensor  "  may  be  proper  enough  in  some 
of  their  applications  and  express  fully  the  action,  but  not  in  all.  Some 
muscles  act  as  flexors  and  extensors  at  the  same  time ;  others  are  exten- 
sors at  one  part  of  the  stride  and  flexors  at  another ;  and  some  of  the 
most  powerful  propellers  in  the  whole  machine  are  flexors,  as  we  shall 
show  in  the  course  of  this  treatise.  It  will  be  seen  that  the  actions 
of  the  muscular  powers  are  sometimes  quite  too  complicated  to  be 
expressed  in  one  word. 

The  term  "  extensor "  is  commonly  applied  to  all  muscles  whose 
action  is  to  enlarge  the  angles  and  by  so  doing  elongate  the  limbs ; 
but  this  extension  may  be  forward  when  the  foot  is  in  the  air,  or  back- 
ward when  the  foot  is  on  the  ground.  There  is  no  word  in  use  by 
anatomists  to  express  the  fundamental  idea,  propulsion.  The  terms 
"  flexion  "  and  "  extension "  will  be  used  in  the  following  pages  to 
express  the  action  of  a  muscle  upon  its  attachments,  without  reference 


38  THE    HORSE   IN    MOTION. 

to  its  functions  in  locomotion.  The  words  "  adductor "  and  "  abduc- 
tor," meaning  the  function  of  drawing  to  or  away  from  the  vertical 
plane  passing  through  the  axis  of  the  body,  are  well  enough,  but  we 
must  not  be  misled  by  the  application  of  these  names  to  muscles  which 
may  have  such  action  to  the  extent  only  of  five  per  cent  of  their  work, 
and  the  rest,  or  eighty-five  per  cent,  devoted  to  propulsion. 

I  have  already  referred  to  the  misnomers  in  muscles  ;  they  mislead 
the  mind  no  less  with  regard  to  their  action  than  to  their  form  and 
construction.  'What  can  be  more  inappropriate  than  the  names  semi- 
membranosus  and  semi-tendinosus,  meaning  half  membrane  and  half 
tendon,  when  applied  to  the  muscles  so  named  in  the  horse  ?  They 
are  well  enough  when  applied  to  the  corresponding  muscles  in  man, 
but  in  the  horse  they  are  not  at  all  membranous  or  tendinous. 

We  should  be  glad  to  dispense  with  names  altogether,  and  apply 
abstract  or  algebraic  terms  to  avoid  misconceptions,  if  practicable,  but 
we  must  use  such  as  are  given,  and,  where  there  are  synonymes,  use 
such  as  are  least  liable  to  the  objection  referred  to. 

There  is  a  group  of  muscles  whose  action  is  to  advance  the  whole 
posterior  extremity  after  the  act  of  propulsion  is  complete.  They  are 
all  deep-seated,  with  two  exceptions. 

1\\Qpsoas  magnus  (Plates  VI.,  VII.,  a,  a)  has  its  origin  in  the  abdo- 
men, along  the  under  surface  of  the  lumbar  vertebra ;  its  fibres,  which 
determine  the  course  of  its  action,  are  directed  backward  and  down- 
ward, and  it  terminates  in  a  long  tendon  which  is  inserted  into  a  rough 
ridge  on  the  inner  side  of  the  femur,  or  thigh  bone,  just  below  the  head 
of  the  bone ;  another  of  this  group  is  the  iliacus  (c,  Plate  VII.),  which 
arises  from  the  lower  face  of  the  ilium,  or  hip.  The  course  of  its  fibres 
is  similar  to  that  of  those  of  the  psoas,  but  its  origin  being  farther  from 
the  median  plane,  its  direction  is  more  inward  to  join  the  last-named 
muscle  at  the  same  point  on  the  inner  face  of  the  femur.  These  two 
muscles  are  of  delicate  organization,  and,  though  differing  in  form,  unite 
in  their  function  of  flexing  the  femur  upon  the  pelvis,  and  so  carrying 
the  whole  leg  forward.  The  iliacus,  having  its  course  more  inward 
than  the  'other,  has  the  effect  of  carrying  the  free  end  of  the  femur  out- 
ward, —  the  "  stifle  action,"  so  important  in  the  trotting  horse. 


b- 


MTTS  C I^E  S    S  HOW  1ST 


'  • '.  t  •• 


\ 


THE    HORSE    IN    MOTION.  39 

The  ten  nor  vagimc  femoris  (Plate  III.,  a,  a)  has  its  fibres  spread 
out  beneath  the  skin  and  the  broad  fascia  of  the  thigh.  It  has  its  fixed 
insertion  in  the  crest  of  the  ilium,  or  hip;  its  fibres  arc  about  eight 
inches  in  length,  and  its  weight  not  less  than  two  pounds;  its  action, 
direct  and  indirect,  is  upon  the  thigh  to  flex  that  bone  upon  the 
pelvis  ;  from  the  shortness  of  its  fibres  its  action  as  a  flexor  cannot 
extend  beyond  three  inches,  but,  being  exerted  at  the  commencement 
of  the  flexion,  when  its  aid  is  most  required,  it  is  very  useful.  It 
is  intimately  associated  locally  and  functionally  with  the  superficial 
glutens,  which  lias  one  of  its  attachments  at  the  hip  bone,  and  an- 
other at  the  thigh  bone,  or  femur,  about  one  third  of  the  distance 
from  its  head.  This  portion,  therefore,  acts  with  the  last  mentioned 
in  flexing  the  thigh;  the  other  branch  extends  alongside  of  the  long 
vastus,  filling  the  angular  space  made  by  that  muscle  where  it  crosses 
the  great  glutens.  (This  is  made  clear  by  Plate  IV.,  where  the  muscle 
under  consideration  is  dissected  away,  along  with  the  tensor  vaginae 
femoris.)  It  will  be  seen  that  it  arises  from  the  spine,  in  front  of  the 
origin  of  the  long  vastus,  v,  v,  v,  and  its  tendinous  insertion  is  at  6, 
or  third  trochanter  of  the  femur  (see  skeleton,  Plate  II.,  6);  the  action 
of  this  division  is  therefore  that  of  an  extensor,  and  directly  over  the 
head  of  the  femur  at  e,  as  we  shall  see  when  we  come  to  consider  the  action 
of  the  posterior  extremity  as  a  unit  in  locomotion.  The  action  of  this 
muscle  has  been  a  controverted  question.  Blain  teaches  that  it  is  a 
flexor  of  the  thigh,  Bourgelot  classes  it  with  the  extensors,  and  Chauveau 
is  of  the  opinion  that  it  is  an  adductor.  This  confusion  has  evidently 
arisen  from  confounding  the  action  of  its  two  branches.  From  these 
two  fixed  insertions,  so  remote  from  each  other,  the  fibres  converge  to 
the  movable  insertion  at  the  ridge  on  the  femur,  as  already  stated, 
about  one  third  down  the  length  of  the  shaft,  and  between  them  the 
fibres  of  the  muscle  are  lost  in  the  fibres  of  the  underlying  muscle  and 
barely  distinguishable  in  the  plate.  The  form  of  this  muscle  has  never 
indicated  its  use  in  locomotion,  but  when  removed,  as  in  Plate  IV.,  its 
value  as  an  element  of  beauty  is  made  apparent. 

The  sartorius  (Plate  VI.,  i>)  of  the  old  authors,  so  called  from  its 
analogue  in  man,  and  so  called  in  man  because  it  is  the  muscle  which 


40  THE    HORSE    IN    MOTION. 

enables  him  to  assume  the  cross-legged  position  of  a  tailor,  is  named 
by  Chauveau  the  long  adductor.  It  has  its  origin  on  the  tendons  of 
the  psoas  muscles  at  a  distance  from  the  mesian  plane  equal,  in  the 
normal  position  of  the  animal,  to  that  of  its  insertion  at  the  inner  head 
of  the  tibia.  The  distance  of  its  corresponding  origin  in  man  would 
carry  it  fully  seven  inches  farther  outward  and  across  the  great  body  of 
the  iliacus  muscle.  Its  action,  therefore,  is  simply  as  a  flexor  of  the 
thigh  upon  the  pelvis,  but  from  its  great  length,  eighteen  inches,  it  has 
a  sustained  action  in  carrying  the  limb  forward  to  a  new  position.* 

There  are  some'  other  small  muscles,  such  as  the  pectincus,  small 
adductor,  etc.,  whose  weight  is  so  inconsiderable,  and  whose  action  is  so 
near  the  centre  of  motion,  that  they  cannot  be  supposed  to  have  any 
special  influence  in  locomotion.  They  are  of  more  interest  to  com- 
parative anatomists,  but  mechanically  they  are  of  small  weight.  The 
action,  such  as  it  is,  seems  to  be  allied  to  the  last,  or  that  of  adduction, 
to  preserve  the  balance  between  the  adduction  and  abduction  of  the 
great  propelling  muscles,  for  it  appears  to  be  true  that  nothing  in  the 
animal  economy  was  made  in  vain,  and  no  vacuum  exists.  When 
the  ancients  propounded  the  law  that  "Nature  abhors  a  vacuum,"  they 
"  builded  better  than  they  knew." 

In  the  complicated  mass  of  muscular  forces  involved  in  each  of  the 
propelling  limbs  of  the  horse,  it  is  impossible  to  determine  whether 
adduction  or  abduction  predominates:  under  the  exercise  of  the  will, 
either  may  do  so ;  but  when  the  mind  of  the  quadruped  is  directed  to 
some  exterior  object,  to  the  attainment  of  which  the  co-ordination  of 
all  the  locomotive  forces  are  necessary,  the  adductor  and  abductor 
action  of  the  muscles  may  be  considered  literally  side  issues,  and  the 

*  Herein  lies  a  curious  conundrum  for  the  Darwinians  of  the  atheistic  school.  If  changes 
were  by  insensible  degrees,  how  did  the  origin  of  this  muscle  become  transported  from  the 
superior  spinous  process  of  the  ilium  in  man,  to  the  tendons  of  the  psoas  muscles  across  that 
body  of  the  defenceless  iliacus  ?  That  it  should  have  been  effected  by  imperceptible  degrees 
seems  entirely  out  of  the  question ;  and  as  there  is  a  doubt  as  to  priority  in  order  of  descent, 
or  ascent  as  the  case  may  be,  we  will  take  the  liberal  side,  and  admit  that  the  two  families, 
Equus  and  Homo,  are  of  equal  age  and  still  evolving,  but  like  parallel  lines  they  can  never  meet ; 
that  the  Equus  can  never  be  so  much  as  a  ninth  part  of  a  Homo,  or  a  Homo  so  much  as  an 
Equus  asinus  without  tangling  his  legs  worse  than  with  a  too  free  use  of  his  favorite  beverage, 
or  an  interchange  of  the  origins  of  the  sartorius. 


a 


THK    HORSK    IN    MOTION.  41 

propelling  forces  alone  are  called  into  play,  and  every  muscle  "of  the 
line  "  has  to  contribute  its  part,  and  the  action  is  automatic. 

The  muscles  not  employed  as  propellers  or  carrying  weight  are 
few  and  small,  as  we  have  seen,  bearing  no  comparison  to  the  others. 
We  will  consider  the  latter  in  their  order,  commencing  with  the  great 
glutens  (Plates  III.,  IV.,  V.,  c,  c,  t,).  It  is  a  muscle  of  the  first  rank. 
As  seen  in  the  plates,  it  reaches  forward  over  the  loins  and  adheres  to 
the  strong  aponeurosis,  or  tendinous  membrane  overspreading  the  ilio 
spinalis.  It  passes  over  the  concave  border  of  the  ilium,  or  ridge 
between  the  hip  and  the  angle  of  the  croup,  covers  the  upper  surface 
of  the  ilium  and  the  ligaments  that  cover  its  openings,  and  is  at- 
tached to  the  spines  of  the  lumbar  vertebra  and  those  of  the  sacrum ; 
it  is  also  attached  to  the  strong  aponeurosis  that  covers  it  externally 
like  all  superficial  muscles  of  the  back.  This  aponeurosis  is  repre- 
sented as  dissected  away  in  the  plate.  Its  fibres  all  converge  outward, 
downward,  and  backward  to  their  insertion  into  the  great  trochanter 
behind  the  head  of  the  bone,  best  represented  in  Plate  V.,  c,  c,  c.  (The 
great  trochanter  is  so  largely  developed  that  it  forms  the  short  arm  of 
a  lever,  bent  at  almost  a  right  angle  to  the  shaft  of  the  bone,  whose 
length  does  not  exceed  four  inches  from  the  head  of  the  bone  as  a 
fulcrum.)  The  length  of  its  longest  fibres  is  twenty-six  inches,  and 
its  average  weight  in  two  well-bred  mares  *  was  found  to  be  sixteen 
pounds.  It  occupies  a  very  advantageous  position  to  give  speed  to  the 
movements  of  the  leg.  The  length  and  volume  of  its  muscular  fibres 
enable  it  to  keep  up  a  sustained  action  from  the  time  the  hind  foot 
takes  the  ground  under  or  in  advance  of  the  centre  of  gravity,  until 
it  leaves  it  after  completing  its  propulsive  effect.  When  the  foot  is 
off  the  ground  it  furnishes  the  sinews  of  war,  offensive  and  defensive. 
The  distance  from  the  insertion  to  the  fulcrum  or  head  of  the  bone 
being  so  short,  it  causes  the  foot  when  free  from  the  ground  to  move 
with  great  velocity. 

•  The  weight  of  the  animal  from  which  the  measurements  and  weights  of  muscles  are  given 
was  about  1,100  Ibs.  These  figures  must  not  be  considered  absolutely  correct,  but  relatively. 
In  a  horse  regularly  worked  the  muscles  will  be  found  to  be  heavier  than  in  the  better  bred  but 
idle  ones  sacrificed  on  the  altar  of  Science. 

6 


42  THE    HORSE    IN    MOTION. 

If  the  reader  will  refer  to  Plate  III.  he  will  see  only  a  portion  of 
this  muscle ;  its  extent  forward  is  concealed  by  the  pearly-colored  apo- 
neurosis  which  completely  covered  it  and  is  only  partially  dissected 
away;  and  by  comparison  with  Plate  VIII.  and  the  skeleton,  Plate  II., 
he  will  find  little  difficulty  in  understanding  the  relations  of  this  muscle 
with  the  surrounding  parts.  In  the 'succeeding  Plate  IV.  the  whole 
outer  face  of  it  is  exposed  except  the  extreme  posterior  border,  which 
is  covered  by  the  long  vastus  muscle  crossing  its  fibres  diagonally;  the 
concavity  in  the  ridge  of  the  ilium  from  b  to g,  Plate  VIII.,  shows  also 
the  aponeurosis  which  covers  the  ilio  spinalis  and  which  serves  as 
a  base  for  the  attachment  of  the  gluteus  forward  of  the  ilium.  At 
Plate  V.,  h,  are  seen  the  attachments  by  tendon  of  the  great  gluteus  to 
the  trochanter.  (See  skeleton,  Plate  II.)  The  centre  of  motion,  or 
head  of  the  femur,  for  the  posterior  limb  is  a  little  in  front  of  this,  lies 
deeper,  and  cannot  be  felt  externally.  This  trochanter,  therefore,  is 
relied  upon  by  horsemen  as  a  point  for  measurement,  and  is  known  to 
them  as  the  "  whirlbone."  Referring  again  to  Plate  VIII.,  the  severed 
tendons  of  the  great  gluteus  may  be  seen  at  c,  c. 

The  deep  gluteus  is  well  shown  at  P,  Plate  VIII.  It  arises  on 
the  shaft  of  the  ilium,  and  its  fibres  follow  the  course  of  that  bone  and 
adhere  to  it  as  they  descend.  Its  muscular  fibres  are  intermingled 
with  tendinous  bands  following  the  same  course,  and  the  insertion  of 
the  muscle  is  into  the  neck  of  the  femur,  or  thigh  bone,  just  outside 
of  the  capsular  ligament.  Its  curious  construction  of  mingled  bands 
of  tendon  and  muscle  gives  it  the  properties  of  both,  the  passive  re- 
sistance of  the  former  and  the  active  aggressive  force  of  muscular  fibre. 
The  spiral  course  of  its  fibres  indicates  that  it  is  intended  to  rotate  the 
leg  outward,  but  more  especially  to  hold  the  head  of  the  femur  in  its 
socket.  Its  influence  in  locomotion  must  be  small. 

The  long  vastus  is  second  only  to  the  great  gluteus  in  weight, 
its  equal  in  length,  and  from  its  great  advantage  of  position  much 
superior  to  it  in  effective  power  to  perform  the  work  required  of 
it.  Its  position  may  be  seen  in  v,  Plates  III.,  IV.,  IX.,  and  in  Plate 
V.  its  absence  is  more  conspicuous  than  its  presence  could  be.  Its 
insertion  is  into  the  external  condyle  of  the  femur  (see  Plates  II. 


, 


-t    MUSCLES   CF  THE    HAUNCH 


1HK    HAUN    :     •  :  HE   SAJRTOH1US  AND    ORA.CIT.iS    MO     CLHS    REMOVED. 


THE   HORSE    IN    MOTION.  43 

and  V.),  and  its  relations  are  so  perfectly  shown  in  the  plates  as  to 
scarcely  require  description.  Plate  IV.  shows  the  superficial  gluteus 
removed  and  the  anterior  margin  of  the  long  vastus  exposed.  It 
has  its  origin  on  spines  of  the  sacrum  posterior  to  those  occupied 
by  the  superficial  gluteus ;  it  fills  the  deep  fossa  anterior  to  the 
tuberosity  of  the  ischium,  and  overlaps  the  hip  joint  four  inches ; 
being  lodged  in  this  deep  fossa,  its  position  is  fixed  at  that  point; 
its  direction  is  then  changed  so  as  to  run  downward  and  forward 
until  it  reaches  the  lower  end  of  the  femur,  where  its  tendon  is  con- 
founded with  that  of  the  patella. 

.\s  thus  described,  the  posterior  branch,  which  is  admitted  by 
anatomists  to  be  distinct  in  structure  and  function,  is  detached.  (It 
is  marked  s'  in  Plate  V.)  This  is  done  for  reasons  which  will  be 
given  when  we  come  to  consider  the  semi-tendinosus.  Its  weight,, as 
so  limited,  is  nine  pounds,  its  length  twenty-six  inches.  The  space 
occupied  on  the  surface  in  front  of  the  tuberosity  of  the  ischium 
is  eight  inches,  or  four  inches  over  the  trochanter  of  the  femur,  and 
the  circumference  of  the  body  of  the  muscle  at  that  point  is  fifteen 
inches. 

It  is  nearly  uniform  in  thickness  throughout,  except  as  its  mus- 
cular fibres  give  way  to  tendinous  ones  toward  its  lower  insertion. 
While  the  great  gluteus  has  some  of  its  fibres  measuring  as  long,  the 
great  mass  of  them,  on  which  its  strength  depends,  are  not  half  that 
length.  The  concentration  of  the  fibres  of  the  gluteus  before  their 
insertion  into  the  trochanter  is  very  great,  and  as  their  power  depends 
upon  their  number  and  not  upon  their  length,  that  of  this  muscle  is 
enormous.  Though  it  acts  on  the  short  end  of  the  lever,  the  line  of 
its  action  is  very  direct.  But  the  vastus  acts  upon  the  extremity 
of  the  long  end  of  the  lever,  and  from  the  great  length  of  its  fibres 
sustains  its  action  for  a  long  time.  These  muscles  hold  a  very 
interesting  relation ;  they  supplement  one  another.  The  power  of 
the  gluteus  is  effective  in  giving  velocity,  as  in  kicking;  that  of 
the  vastus  is  effective  in  pushing  the  body  over  the  foot  on  the 
corresponding  side,  when  it  is  fixed  upon  the  ground,  as  in  rearing 
and  leaping ;  in  the  hare,  whose  mode  of  progression  is  by  a  sue- 


44  THE    HORSE    IN    MOTION. 

cession  of  bounds,  it  is  developed   enormously  in  comparison  with 
the  gluteus. 

The  semi-tendinosus  is  represented  in  Plates  III.,  V.,  IX.,  s,  s,  s, 
where  its  situation  is  shown  immediately  behind  the  vastus.  It 
has  two  origins,  one  from  the  sacral  spines  and  the  first  of  the  tail 
bones  or  their  ligaments,  the  other  from  the  lower  face  of  the 
ischium  (Plate  V.,  i),  below  which  they  unite.  It  divides  into  three 
branches;  the  central  is  attached  to  the  strong  fascia  covering  the 
muscles  of  the  calf,  the  other  two  reach  forward  to  be  attached  to 
the  same  common  fascia,  one  on  the  inner  and  the  other  on  the 
outer  face  of  the  leg;  the  latter  is  spread  out  as  far  forward  as  the 
insertion  of  the  long  vastus ;  the  inner  to  a  corresponding  position 
on  the  inner  face.  These  lateral  branches  overlay  the  muscles  of 
the  calf,  or  gastrocnemii,  and  give  that  compressed  form  that  distin- 
guishes the  calf  of  the  horse's  leg.  It  is  a  powerful  muscle.  Its 
weight  is  eleven  pounds.  The  distance  of  its  origin  at  the  spine 
to  its  insertion  at  the  head  of  the  tibia  is  twenty-eight  inches. 
The  part  of  the  muscle  which  has  its  origin  at  the  ischium,  to  the 
same  point  of  insertion,  is  nineteen  inches,  and  its  greatest  circum- 
ference is  ten  inches. 

The  action  of  this  muscle  cannot  be  represented  by  any  abstract 
terms.  It  has  two  functions :  it  lifts  the  leg  when  the  act  of 
propulsion  is  complete,  flexing  the  leg  upon  the  thigh  until  the 
line  perpendicular  from  the  centre  of  motion  is  passed,  when  it 
relaxes,  while  the  extensor  proper  of  the  leg,  the  triceps  femoris  (/,  /), 
carries  the  foot  to  a  new  position  in  advance.  As  soon  as  the  foot 
is  upon  the  ground  and  the  limb  feels  the  weight  thrown  upon  it, 
then  the  full  power  of  this  muscle  is  called  into  play,  no  longer 
a  flexor,  and  not  as  an  extensor,  nor  even  as  a  propeller,  but  as  a 
supporter,  which  character  it  performs  until  the  direction  of  its  fibres 
passes  the  perpendicular,  when  they  cease  to  act  until  the  next  stride 
begins,  so  that  when  the  foot  is  off  the  ground  in  the  first  quarter 
of  the  stride  it  is  a  flexor;  it  is  inactive  in  the  second  quarter, 
and  a  supporter  in  the  third,  while  it  plays  no  part  in  the  fourth. 
The  importance  of  the  proper  understanding  of  the  action  of  this, 


STERIOR    EXTREMITY"  EXPO  SING-  THE  DEEPEST  MUSCLES   OF   THE   HAUNCH. 


THE    HORSE    IN    MOTION.  45 

as  of  other  muscles  of  the  haunch,  will  be  appreciated  when  we  come 
to  the  consideration  of  the  fast  paces. 

The  external  branch  of  the  semi-tendinosus  has  by  all  anatomists 
been  claimed  as  the  posterior  part  of  the  vastus,  while  it  was  admit- 
ted to  be  anatomically  and  functionally  distinct.  There  is  really  no 
relation  between  them  except  in  their  juxtaposition  and  in  their  super- 
ficial appearance.  Their  connection  is  by  a  thin  layer  of  cellular 
tissue,  while  the  connection  between  the  branch  in  question  and  the 
semi-tendinosus  is  most  intimate,  the  partition  being  an  aponeurosis 
to  which  both  are  attached,  as  in  penniform  muscles,  from  which  it 
is  impossible  to  separate  the  muscular  fibres  without  laceration.  I 
have  no  doubt  that  the  point  will  be  conceded  by  all  anatomists  when 
their  attention  is  called  to  it,  especially  since  it  is  shown  that  the 
annexation  I  propose  makes  a  complete  organ  of  the  semi-tendinosus, 
with  all  its  parts  acting  in  perfect  accord. 

The  semi-membranosus  adjoins  the  last-described  muscle  and  is 
concealed  by  it  in  Plate  V.  Their  relation  is  seen  in  the  posterior 
view,  Plate  IX.,  /.  This  muscle  also  has  two  origins  like  the  last, 
but  that  at  the  spine  is  by  a  thin  tendon,  and  this  branch  is  small 
(Plate  VI.,  a).  The  great  mass  of  the  muscle  (/,  Plate  VII.)  arises 
from  the  lower  surface  of  the  ischium  (Plate  VII.,  c].  It  is  thin  pos- 
teriorly where  it  overlaps  the  semi-tendinosus  (at  /,  Plate  IX.),  but  be- 
comes thick  where  it  unites  with  the  so-called  great  adductor  (g,  Plate 
VII.).  The  lower  insertion  is  broad,  the  posterior  portion  of  it  is  into 
the  fascia  of  the  leg,  and  the  anterior  by  tendon  along  with  that  of  the 
great  adductor  into  the  interior  condyle  of  the  femur  opposite  that 
of  the  vastus ;  its  weight  is  six  pounds.  The  thin  posterior  portion 
of  the  muscle  acting  on  the  fascia  of  the  leg  flexes  it  like  the  semi- 
tendinosus,  but  the  great  mass  of  it  acts  in  unison  with  the  great 
adductor  (g,  Plate  VII.),  with  which  it  is  so  closely  united  that  it  is 
difficult  to  separate  them. 

The  great  adductor  also  rises  from  the  ischium  in  front  of  the 
last  described,  and  is  inserted  into  the  internal  condyle  of  the  femur; 
its  weight  is  three  and  a  half  pounds,  and  its  fibres  are  fifteen  inches 
in  length,  though  fibres  are  thrown  off  along  its  course  to  the  femur, 


46 


THE    HORSE    IN    MOTION. 


on  which  it  acts  as  an  adductor  when  the  animal  is  at  his  ease,  but  the 
joint  action  of  these  two  muscles  is  as  supporters.  They  have  no 
attachments  forward  of  the  centre  of  motion  at  the  head  of  the  femur, 
but  like  the  semi-tendinosus  they  permit  the  limb  to  be  advanced  to 
the  extended  position  to  support  the  centre  of  gravity,  and  then,  in 
common  with  all  the  great  muscles  of  the  posterior  extremity,  they 
support  the  whole  weight  of  the  body,  and  then  only  for  a  limited  time 
do  they  act  as  extensors.  This  will  be  better  understood  when  we 
analyze  the  movements  in  the  gallop. 

There  is  only  one  other  muscle  of  the  thigh  which  we  will  notice, 
\hzgracilis  (Plate  VI.,  m).  (It  is  dissected  away  in  Plate  VII.)  It  is 
superficial  on  the  face  of  the  thigh,  and  is  nearly  as  broad  as  it  is  long. 
It  has  its  origin  on  the  symphasis  of  the  pubis  where  it  meets  its 
fellow  of  the  opposite  side.  It  is  about  an  inch  in  thickness  in  the 
centre,  thins  off  each  way,  and  is  attached  to  the  fascia  of  the  leg 
for  a  distance  corresponding  to  its  origin  at  the  pubis.  It  corre- 
sponds to  the  gracilis  in  man,  and  is  called  by  Chauveau  the  short 
adductor.  Its  weight  is  about  two  and  a  half  pounds.  The  course 
of  its  fibres  is  downward  and  about  five  degrees  outward.  In  its 
contraction  the  force  is  as  an  adductor  about  ten  per  cent,  but  as  a 
supporter  to  the  weight  of  the  body  when  it  rests  on  one  foot  its  value 
is  not  to  be  overlooked. 

The  want  of  knowledge  of  the  action  of  the  limbs  in  locomotion 
has  led  the  student  of  anatomy  into  a  too  circumscribed  view  of  the 
action  of  the  muscles.  It  has  led  him  to  give  first  consideration  to 
forces  of  secondary  importance.  It  will  be  seen  by  a  general  view  of 
all  the  muscles  of  the  haunch  that  those  acting  upon  the  thigh  bone, 
or  femur,  from  above  are  inserted  on  the  outer  face  of  the  bone,  while 
those  from  the  lower  surfaces  of  the  pelvic  bones  are  inserted  into  the 
inner  face  of  the  femur.  The  primary  object  in  both  is  locomotion,  but, 
from  the  indirect  manner  of  the  application  of  the  forces,  they  are  all 
necessarily  compound ;  for  example,  the  great  gluteus  acts  as  a  pro- 
peller and  adductor,  while  the  great  adductor  acts  as  a  propeller  and 
adductor,  the  Eduction  of  one  being  compensation  for  the  seduction 
of  the  other.  In  a  humanly  constructed  machine,  as  a  locomotive, 


* 


•     '. 


H   VIEW  OF  THE    MUSCLES    OF    THE   HAUNCH. 


rmn-x 


THE    HORSE    IN    MOTION.  47 

where  the  angles  are  right  angles,  and  the  application  of  power  is  direct, 
there  is  less  need  of  composition  of  forces ;  but  the  design  of  nature 
was  higher:  beauty  was  superadded  to  power,  and  for  this  end  great 
sacrifices  of  power  were  made.  Though  difficult  of  demonstration,  it 
may  be  taken  for  granted  that  at  full  speed  the  adduction  and  abduc- 
tion of  all  the  muscles  in  action  counterbalance  each  other;  if  they  did 
not,  either  the  feet  would  interfere  or  they  could  not  be  brought  to 
support  the  centre  of  gravity,  and  in  either  case  the  animal  might  fall. 

How  is  it  possible  for  the  student  to  learn  the  action  of  the  machine 
when  the  muscular  forces  are  represented  as  chiefly  composed  of 
adductors  and  abductors,  as  if  the  animal  was  designed  to  move  side- 
wise  like  a  crab  ?  These  names  may  be  perfectly  proper  to  express 
the  action  of  their  analogues  in  man ;  for  man,  of  all  his  relations,  has 
the  most  inefficient  locomotive  apparatus,  but  the  greatest  diversity  of 
action  in  his  extremities. 

Leaving  the  muscles  of  the  haunch,  we  descend  to  those  of  the  leg. 

The  triceps  fcmoris  (Plates  III.,  IV.,  V.,  IX.,  /,  f)  is  the  great 
muscle  that  occupies  the  front  of  the  thigh.  As  its  name  implies,  it 
has  three  heads.  The  middle  one  has  its  upper  insertion  in  the 
smooth  facet  of  the  pubis,  directly  above  the  acetabulum,  or  cup,  in 
which  the  head  of  the  femur  rests  (Plate  II.,  6),  and  is  called  the 
rcctns.  The  other  two  heads  are  attached  to  the  broad  face  of  the 
femur,  as  close  as  possible  to  the  head  of  the  bone  without  inter- 
fering with  its  free  action.  Its  length  is  eleven  inches  only,  but 
its  circumference  is  twenty,  and  its  weight  nine  pounds.  It  cannot 
parated  into  distinct  muscles,  and  it  acts  as  a  unit  in  extend- 
ing the  leg  forward  through  the  patella,  or  knee  cap,  its  point  of 
insertion  ;  but  the  rectus,  or  middle  head,  being  attached  to  the  pel- 
vis, has  the  power  of  moving  the  femur  on  which  it  lies,  as  well  as  of 
extending  the  leg  in  common  with  its  fellows,  so  that  the  action  is  to 
extend  both  bones  on  a  line  forward  ;  but  the  patella  is  not,  like  that  in 
man,  a  part  of  the  knee,  or  articulation,  between  the  femur  and  the  tibia; 
it  has  a  place  of  its  own.  The  front  portion  of  the  lower  extremity  of 
the  femur  is  elevated  or  built  up,  and  furnished  with  a  trochlea,  or 
grooved  surface,  with  cartilage  and  synovial  membrane,  expressly  for 


48  THE    HORSE    IN    MOTION. 

the  patella  to  play  on  as  over  a  pulley ;  the  tendon  of  the  triceps,  after 
being  inserted  into  the  patella,  is  extended  beyond  it  to  be  inserted  into 
a  rough  tubercle  in  the  head  of  the  tibia.  Anatomists  call  the  portion 
below  the  patella,  ligament.  Physiologists  may  say  that  the  patella  is 
developed  in  the  tendon.  We  will  not  discuss  the  question.  It  is  to 
us  as  if , the  bone  was  developed  in  the  tendon  as  it  is  developed  in  ten- 
dinous fibres  elsewhere,  and  the  ligament  below  the  patella  does  the 
same  office  as  the  tendon  above.  The  force  of  this  powerful  muscle 
as  determined  by  its  circumference  can  only  be  compared  to  the  great 
gluteus,  and  is  called  into  action  after  the  extreme  of  flexion  has  been 
passed,  and  the  femur  has  been  brought  forward  by  its  flexors  already 
referred  to,  and  in  which  the  rectus  may  have  borne  a  part.  After  the 
foot  has  taken  the  ground  it  steadies  the  stifle,  or  knee,  and  regulates 
the  flexion  of  that  joint  as  the  angles  close  to  shorten  the  limb.  After 
the  perpendicular  is  passed,  it  again  resumes  the  offensive  and  extends 

g 

the  leg  in  giving  the  propulsive  impulse,  which  it  maintains  to  the 
close  of  the  stride.  It  rests,  therefore,  but  for  one  fourth  of  a  stride, 
and  if  the  rectus  acts  as  a  flexor  of  the  thigh  at  the  same  time  with 
the  flexors  of  the  thigh  upon  the  pelvis  it  has  but  little  rest. 

The  gastrocnemii  (Plate  VIII.,  in,  m),  or  superficial  muscles  of  the 
calf,  hold  a  corresponding  position  on  the  leg  to  that  of  the  triceps  on 
the  thigh,  as  well  as  to  the  levers  on  which  they  act;  but  while  the 
action  of  the  triceps  is  very  simple  and  easily  comprehended,  that  of 
the  muscles  of  the  calf  is  very  complicated,  and  can  only  be  understood 
by  a  study  of  the  whole  limb  as  a  machine  of  which  the  voluntary 
muscles  form  a  part.  Whether  it  will  be  possible  for  me  to  interpret 
the  action  of  the  muscles  and  the  use  of  the  tendons  with  their  checks 
and  reinforcements  without  the  actual  limb  before  us  is  a  question  to 
be  determined.  An  attempt  was  made  to  represent  the  parts  by  the 
aid  of  the  camera,  but  the  results  were  not  satisfactory.  Plate  X.  is 
from  a  careful  drawing  by  Hahn.  The  gastrocnemius  of  the  right  side, 
g,  is  dissected  away  from  its  origin  in  the  femur  and  raised  by  hooks 
to  show  the  perforatus  tendon,/.  This  tendon  is  inserted  into  the 
femur  about  two  inches  from  the  joint,  along  with  the  gastrocnemii 
muscles.  It  has  a  muscular  body  of  its  own,  not  distinguishable  in 


e 


THE    HOKSF.    IN    MOTION.  49 

the  drawing,  being  there  confounded  with  the  body  of  the  muscle  lying 
upon  it.  On  their  way  to  their  insertion  into  the  point  of  the  hock  the 
tendons  of  these  two  muscles  are  twisted  upon  each  other  half  round,  so 
that  the  pcrforatus  tendon,  which  was  beneath,  reaches  its  insertion  at 
the  outside  of  that  of  the  gastrocnemius.  The  tendon  of  the  latter  is 
fixed  immovably  to  the  bone,  and  acts  to  extend  the  metatarsus  below 
it,  but  the  tendon  of  the  pcrforatus  passes  over  the  point  of  the  hock, 
where  it  is  provided  with  a  pulley  similar  to  that  at  the  knee,  over 
which  it  glides  to  a  very  limited  extent,  being  strongly  secured  by  liga- 
ments to  the  point  of  the  hock,  /i;  it  then  passes  down  behind  the 
metatarsus,  or  cannon  bone,  to  the  pastern,  or  fetlock  joint,  where  it 
throws  out  a  ring  to  encircle  the  tendon  of  the  perforans,  as  seen  at 
r.  (These  two  tendons,  forming  the  "  back  sinews,"  would  be  liable, 
from  the  extreme  flexions  and  extensions  which  take  place  at  that 
joint,  to  be  dislocated,  but  for  the  extraordinary  provisions  made  to 
prevent  it.)  It  then  passes  to  its  insertion  into  the  bones  of  the  foot. 
When  the  knee  is  flexed,  as  in  the  plate,  this  tendon  (perforatus), 
being  inserted  into  the  femur  above  the  knee  joint,  is  relaxed,  and  the 
extensors  of  the  foot,  which  are  located  in  front  (a),  are  permitted  to 
straighten  or  extend  the  foot,  as  may  be  seen  in  all  the  plates  where 
the  hind  foot  is  in  the  act  of  taking  the  ground  ;  but  when  the  leg  is 
extended  upon  the  thigh  the  tendon  is  drawn  upward,  and  flexion  at 
the  joints  of  the  foot  is  effected,  the  extensors  at  a  offering  no  oppo- 
sition, so  that  extension  of  the  superior  joints,  as  in  the  act  of  propul- 
sion, causes  flexion  of  the  inferior.  This  movement  is  independent 
of  muscular  action,  and  may  be  shown  in  the  dead  subject,  except  so  far 
as  the  act  of  the  extensor  of  the  foot  (extensor  pedis,  a),  is  concerned ; 
but  the  spindle-form  body  of  the  perforatus  muscle  connected  with  the 
tendon  contracts  by  volition,  and  flexes  the  foot  with  its  added  force. 

If  we  consider  the  limb  in  the  position  as  given  in  the  plate,  and 
then  forcibly  extend  the  foot  until  the  pastern  joint,  S,  is  in  the  posi- 
tion it  takes  when  the  horse  is  standing,  the  tendon,  /,  will  become 
tense,  and  also  the  ligaments  that  limit  its  motion  at  the  point  of  the 
hock,//;  beyond  that  it  cannot  be  moved  by  any  force  that  we  can 
apply  short  of  breaking.  It  is  tied  by  the  ligaments  at  the  apex  of 


50  THE   HORSE    IN    MOTION. 

the  hock;  and  if  the  knee  and  hock  joints  are  both  extended  it  will 
not  change  the  relations,  for  the  tendon,  c,  m,  and  the  shaft  of  the 
tibia,  n,  k,  being  parallel,  and  the  distance  from  the  hock  joint,  n,  to 
the  apex  of  the  hock,  c,  and  that  from  the  centre  of  motion,  /£,  at 
the  knee  to  the  insertion  of  the  tendon  at  the  femur,  m,  being  equal 
and  parallel,  they  form  a  parallelogram,  and  changes  in  the  angles, 
as  in  flexion  and  extension,  will  not  affect  the  length  of  its  sides. 
When  the  knee  or  the  hock  joint  is  flexed  or  extended,  the  other 
must  follow.  When  the  horse  is  standing,  and  the  knee  joint  is  ex- 
tended, as  well  as  the  hock,  the  horse  rests  mechanically  upon  the 
tendons,  but  the  knee  is  extended  by  the  triceps,  b,  whose  tension 
requires  an  effect  of  the  will  and  tires  in  time,  so  that  we  see  him 
when  at  his  ease  rest  on  his  hind  legs  alternately,  which  he  never 
does  with  his  fore  foot,  except  when  one  of  them  is  lame. 

The  perforans  muscle,  which  is  so  intimately  related  to  the  last 
has  its  origin  below  the  knee  joint  and  on  the  upper  and  posterior 
face  of  the  tibia  and  fibula,  below  the  popliteus  (Plate  X.,  e\  and  its 
action  is  not  influenced  by  the  flexions  of  that  joint.  Its  tendon  takes 
a  more  direct  course  to  its  insertion ;  it  passes  through  a  groove  at  the 
base  of  the  calcaneum,  near  «,  on  its  inner  side  and  as  near  the  joint  as 
possible.  Strong  ligaments  cover  the  groove  where  the  course  of  the 
tendon  is  changed,  to  prevent  its  displacement.  It  then  passes  down 
behind  the  metatarsal  bone  and  inside  the  tendon  of  the  perforate 
On  its  course  it  receives  the  tendon  of  another  small  flexor,  and  fror 
the  posterior  surface  of  the  metatarsus  an  auxiliary  tendon  or  ligament 
of  nearly  its  own  size.  In  the  plate  this  branch  is  shown  relaxec 
The  tendon,  thus  reinforced,  is  of  twice  the  size  it  was  before  the 
union,  and  passes  above  the  pastern  through  the  ring,  r,  of  the  perfc 
ratus,  and  is  inserted  into  the  bones  of  the  foot. 

This  muscle,  being  entirely  independent  of  the  femur  and  the 
muscles  attached  to  it,  may  flex  the  foot  independently,  and  does  so  ii 
propulsion  in  the  last  part  of  the  stride,  and  also  in  the  same  contrac- 
tion aids  by  its  pressure  at  the  back  of  the  hock  in  extending  that 
joint,  thus  extending  one  joint  while  it  flexes  another.  When  the  foot 
rests  in  the  standing  position,  the  auxiliary  tendon,  t,  above  mentioned 


THE    HORSE    IN    MOTION.  51 

converts  the  part  below  it  into  a  continuous  tendon,  which  performs 
the  office  of  a  ligament,  in  common  with  that  of  the  perforatus,  to 
aid  the  suspensory  ligament  in  supporting  the  weight  of  the  body  in 
the  extreme  extension  which  the  pastern  undergoes  when  the  centre 
of  gravity  is  over  it,  as  in  rapid  locomotion. 

Muscular  fibres  are  found  by  anatomists  scattered  through  the 
tendons  below  the  hock ;  but  for  all  mechanical  purposes  the  sources 
of  power  are  above  and  away  from  the  extremities,  where  the  velocities 
are,  at  times,  more  than  twice  that  of  the  body  and  the  momentum 
must  be  arrested  at  every  stride.  The  hock  in  quadrupeds  represents 
the  heel  in  man,  and  the  elongations  of  bones  and  corresponding 
tendons  are  necessary  modifications  of  the  plan  for  the  development 
of  speed. 

There  is  a  group  of  small  muscles  which  form  what  is  called,  by 
some  horsemen,  the  second  thigh  ;  they  are  on  the  outer  face  of  the 
thigh  and  below  the  stifle,  or  knee,  and  in  front  of  the  calf.  The 
perforans  (d,  Plate  X.)  is  in  this  group,  occupying  the  intermediate 
place. 

The  flexor  of  the  metatarsus  has  its  upper  attachment  on  the 
tibia,  in  front  of  the  perforans,  and  its  lower  in  the  metatarsus,  below 
the  joint,  after  passing  under  the  annular  ligament.  It  is  minutely 
described  by  Chauveau.  It  flexes  the  hock  joint  and  is  a  feeble  an- 
tagonist to  the  gastrocnemii,  but  only  acts  when  the  foot  is  off  the 
ground. 

The  lateral  and  anterior  extensors  occupy,  as  their  names  indicate, 
spaces  on  the  tibia  in  front  of  the  latter,  and  their  tendons,  after  passing 
under  the  annular  ligament,  in  front  of  the  hock,  descend  to  be  in- 
serted into  the  anterior  face  of  the  foot ;  they  act,  therefore,  to  flex  the 
hock  and  extend  the  foot,  raising  the  toe  as  the  limb  is  thrust  forward 
to  take  the  ground. 

The  suspensory  ligament  is  one  of  the  most  wonderful  contrivances 
in  the  whole  locomotive  machinery  of  the  horse.  Though  a  ligament 
only,  with  its  action  beyond  the  control  of  the  will,  it  is  no  less  an  active 
organ,  whose  function  is  indispensable  to  locomotion,  and  the  interest 
in  it  has  been  much  increased  by  the  developments  of  the  camera. 


52  THE    HORSE    IN    MOTION. 

It  is  not  necessary,  in  order  to  consider  the  relations  and  functions 
of  this  organ,  that  we  should  enter  into  a  detailed  account  of  all  the 
ligaments  of  the  foot;  they  are  very  numerous.  Anatomists  limit  the 
name  to  the  strong  band  that  has  its  upper  attachment  to  the  meta- 
tarsus below  the  hock,  and  its  lower  one  into  the  sesamoid  bones,  and 
they  have  given  the  name  of  sesamoid  ligament  to  that  continuation 
from  those  bones  to  the  foot.  We  will  not  discuss  with  anatomists  the 
question  of  their  identity,  but,  mechanically  considered,  they  arc  one, 
and,  like  the  patella,  the  sesamoid  bones  may  be  said  to  be  developed 
in  the  ligament.  If  the  name  were  limited  to  the  first,  it  would  be  a 
misnomer;  for,  to  suspend  the  weight  that  is  thrown  upon  it,  it  is 
necessary  that  a  counter  force  should  act  upon  the  opposite  border  of 
the  sesamoid  bones  equal  in  strength  to  that  above  it.  If  either  part 
were  divided,  the  other  would  have  no  function,  but  united  they  con- 
stitute an  instrument  that  often  bears  the  weight  of  the  whole  body. 
It  is  a  broad,  thick  band,  resembling  tendon,  and  may  be  felt  above  the 
fetlock  between  the  splint  bones  and  the  tendons  of  the  perforatus 
and  perforans  or  "  back  tendons."  This  ligament  fixes  the  sesamoid 
bones  in  the  position  above  and  behind  the  articulation  of  the  first  and 
second  metatarsals,  so  that  when  the  second  metatarsal  or  pastern 
bone  is  thrown  out  from  under  the  first  metatarsus  they  are  drawn 
into  its  place,  and,  their  articular  surfaces  forming  an  arc  of  the  same 
circle,  the  loss  of  the  pastern  is  not  felt ;  but  the  sesamoids  now  bear 
the  whole  weight  of  the  body,  and  they  have  no  support  but  the  sus- 
pensory ligaments  in  which  they  are  imbedded,  and  the  tendons  of  the 
perforans  and  perforatus,  which  cross  the  bridge  between  the  sesa- 
moids. The  perfect  equilibrium  between  the  strength  of  the  ligament 
and  the  force  it  is  required  to  resist  is  of  the  utmost  importance. 
When  the  horse  is  standing  upon  all  four  feet,  the  weight  is  equally 
distributed,  and  the  angles  formed  by  the  pasterns  with  the  bones 
above  are  small,  for  the  weight  upon  each  one  is  not  great  enough  to 
spring  it  far;  but  in  running,  the  whole  weight  in  every  stride  is 
borne  by  each  foot  in  turn  for  a  short  time,  and  the  elasticity  and 
strength  of  its  suspensory  ligament  must  be,  with  that  of  its  reinforc- 
ing tendons,  just  equal  to  its  requirements  to  support  the  body,  for 


THK    HORSE    IN    MOTION.  53 

they  are  all  placed  beyond  the  control  of  the  will.  If  it  yields  too 
much,  the  fetlock  is  liable  to  strike  the  ground  ;  if  it  is  too  rigid  and 
it  does  not  yield  enough,  there  will  be  stiffness  and  a  hobbling  gait. 
\Ve  shall  have  occasion  to  refer  to  this  again  when  we  analyze  the 
paces. 

There  is  no  one  fact,  brought  out  by  the  experiments  of  Mr.  Stan- 
ford with  instantaneous  photography,  of  more  interest  than  the  action 
of  the  suspensory  ligament. 

When  the  horse  is  standing,  it  will  be  seen  that  the  pastern  forms 
an  acute  angle  with  the  metatarsus.  Its  position  indicates  the  length 
of  the  ligaments,  and  it  is  their  resistance  that  prevents  the  further 
extension  of  the  joint ;  but  in  running  and  fast  trotting,  this  ligament 
is  put  upon  the  stretch,  when  the  limb  is  shortened  by  the  weight  of 
the  body,  to  such  an  extent  that  the  pastern  is  made  to  take  a  position 
at  right  angles  to  the  metatarsus  and  horizontal  with  the  ground.  (See 
the  plates  of  horses  speeding,  passim.)  Elongation  of  the  limb  begins 
immediately  after  the  perpendicular  is  passed,  and  as  the  fetlock  was 
the  last  joint  to  reflex  in  shortening,  so  it  is  the  first  to  recover  its 
normal  extension.  This  spring  continues  its  action  during  the  rest 
of  the  stride,  straightening  the  fetlock  joint  as  the  leg  becomes  elon- 
gated after  the  passage  over  it  of  the  centre  of  gravity,  still  sustain- 
ing the  body  with  undiminished  force  until  it  leaves  the  ground,  when, 
being  relieved  from  the  superimposed  weight,  the  flexor  muscles  re- 
gain control ;  and  it  is  the  reaction  of  these  ligaments,  with  that  of 
the  flexor  tendons  acting  as  ligaments,  that  produces  the  quick  move- 
ment, quicker  than  is  possible  in  muscular  contraction,  which  causes 
the  feet  to  throw  dirt ;  it  is  effected  after  the  weight  is  off  the  foot 
and  the  propulsive  effort  is  complete.  There  is  no  muscular  action 
en  the  foot  until  after  the  pressure  is  removed  and  the  flexors  regain 
control. 

It  is  an  exceedingly  difficult  problem  to  determine  the  absolute,  or 
even  the  relative,  work  performed  by  the  different  muscular  powers 
employed  in  locomotion.  There  are  many  different  elements  entering 
into  the  calculation,  that  are  impossible  to  be  weighed.  Muscles 
differ  in  quality  as  well  as  quantity ;  some  contain  a  larger  proportion 


54  THE   HORSE  IN   MOTION. 

of  cellular  or  fibrous  tissue  than  others,  and  will  have  less  power,  other 
things  being  equal.  For  example,  the  glutens  and  vast  us  are  coarse 
muscles  capable  of  resisting  external  force,  and  therefore  popularly 
believed  to  be  strong ;  but  it  is  in  a  meaning  corresponding  to  tough- 
ness, and  that  quality  depends  upon  the  amount  of  interstitial  cellular 
tissue  they  contain,  which  tissue  has  no  contractile  property,  and  can- 
not originate  motion;  while  the  psoas  and  iliacus,  having  but  little 
such  cellular  or  fibrous  tissue,  have  little  power  to  resist  external  force, 
but  have  a  larger  contractile  power  as  measured  by  the  areas  of  their 
sections. 

Muscles  do  not  often  have  their  force  concentrated  at  both  extremi- 
ties, but  it  is  distributed  over  the  face  of  their  levers  at  different  dis- 
tances and  at  different  angles,  as  in  penniform  muscles,  and  nearly  all 
others  in  a  greater  or  less  degree,  and  at  different  angles  at  each  change 
in  the  position  of  the  levers.  Though  we  recognize  the  same  general 
mechanical  principles,  we  cannot  apply  the  same  mathematical  rules 
usual  in  mechanics ;  add  to  these  elements  of  uncertainty  the  com- 
position of  forces  often  in  the  same  muscle,  and  we  see  how  for- 
midable are  the  difficulties  in  the  way  of  reducing  animal  mechanics 
to  an  exact  science. 

But  while  we  cannot  accurately  determine  the  forces  in  detail,  we 
can  in  the  aggregate.  We  see  all  these  different  and  often  antago- 
nistic forces  united  in  their  action  around  a  common  centre  of  motion, 
as  the  hip  joint,  to  effect  one  result.  There  are  certain  general  princi- 
ples, however,  that  we  can  deduce  from  the  facts  before  us.  In  order 
that  the  foot  shall  reach  the  ground  as  far  in  advance  as  possible,  to 
support  the  centre  of  gravity  as  early  as  may  be,  and  as  long  as  pos- 
sible, and  that  it  may  use  its  propulsive  force  later,  it  is  necessary 
that  it  should  be  possessed  of  sufficient  length  ;  but  it  is  bearing  a 
burden  whose  weight  we  will  suppose  to  be  a  thousand  pounds,  and 
going  at  the  rate  of  twenty  miles  an  hour,  and  the  momentum  is  the 
product  of  that  weight  multiplied  by  the  velocity.  This  is  a  respon- 
sibility that  could  not  be  borne  on  stilts.  The  difficulty  is  overcome 
by  so  constructing  the  whole  limb  that  it  shall  be  extensible,  thus 
having  all  the  advantage  of  length  without  its  disadvantage ;  and  the 


THK    IloRSi:    IN    MOTION.  55 

centre  of  motion  is  actually  lowered  several  inches  that  its  practical 
length  may  be  increased.  For  this  purpose  the  system  of  levers  is 
iiM'd,  which,  by  their  flexion  and  extension,  practically  shorten  and 
lengthen  the  limb.  The  acutcness  of  the  angles  at  which  these  bones 
intersect  each  other  is,  therefore,  an  important  element  in  the  mechan- 
ical action  ;  the  angles  to  be  acute  require  long  levers,  and  long  levers 
-Mtate  long  and  powerful  muscles  to  "man"  them.  These  quali- 
ties must  be  bred. 

Flexibility  of  articular  ligaments  may  be  acquired  by  early  training 
and  regular  exercise,  but  the  proportions  of  the  body  are  inherited. 
Length  of  muscular  fibres  and  acute  angles  of  the  levers  on  which  they 
act,  give  sweep  of  limb,  and  strength  depends  upon  the  number  of  them, 
and  the  effective  power  of  both  depends  upon  the  will  or  courage ;  but 
all  these  qualities  would  be  vain  if  the  motion  of  the  extremities  were 
not  so  co-ordinated  that  their  functions  should  be  performed  without 
interference  one  with  another. 

When  the  speed  of  the  horse  is  twenty-five  miles  an  hour  the  rate 
of  the  hind  foot  in  passing  that  on  the  ground  is  twice  that,  or  fifty 
miles  an  hour.  It  is  even  greater  than  that,  for  the  velocity  of  the  foot 
in  its  stride  is  an  accelerated  one  during  most  of  the  distance,  and  may 
be  supposed  to  be  most  rapid  midway.  Now  the  movements  of  the 
posterior  extremity  on  its  centre  are  controlled  by  voluntary  muscles, 
liable  from  various  causes  to  be  irregular,  as  they  must  necessarily  be 
from  the  ever-changing  centre  of  gravity  which  it  is  designed  to  sup- 
port. There  would  have  been  danger  of  one  foot  striking  the  other  leg 
in  passing,  —  an  accident  technically  called  interference,  —  but  another 
danger  still  greater  existed  at  the  stifle  from  the  blows  that  joint  would 
be  liable  to  give  the  abdomen  in  its  extreme  and  violent  flexions.  It 
is  the  duty  of  the  iliacus  muscle  to  guard  the  abdomen  from  this  vio- 
lence, and  when  it  performs  its  office  well,  it  gives  the  "  stifle  action  " 
so  much  admired ;  but  while  the  upper  end  of  the  leg  (tibia)  is  thrown 
out  in  this  action,  the  lower  end  is  correspondingly  thrown  in,  and  the 
foot  would  be  still  more  so  but  for  the  unique  construction  of  the  hock 
joint.  .The  interlocking  grooves  of  this  joint  are  not  direct,  as  in  other 
hinge  joints  of  the  body,  and  as  the  corresponding  joint  in  man  is,  but 


56  THE    HORSE    IN    MOTION. 

oblique,  so  that  when  flexion  takes  place  at  that  joint,  the  lower  ray 
is  carried  obliquely  outward,  and  when  the  other  leg  is  passed,  and  the 
extension  takes  place  again,  its  action  is  reversed,  and  the  foot  is 
returned  to  the  position  required  to  support  the  centre  of  gravity. 
By  this  simple  contrivance  the  danger  of  this  accident  is  placed  beyond 
the  will  of  the  animal,  and  in  well-formed  horses  beyond  the  possibility 
of  accident.  Some  horses  circumduct  the  hind  feet  more  than  others, 
and  in  others  the  stifle  action  is  most  marked ;  but  it  is  not  common 
to  see  both  excessive  in  the  same  horse. 

There  is  often  considerable  difference  in  different  horses  in  the 
length  of  the  hock.  The  long  hock  gives  the  greatest  power,  for  the 
reason  that  the  leverage  is  greater;  but  what  is  gained  in  power  is 
lost  in  speed. 

Sometimes  there  is  a  looseness  in  the  articulations  of  the  tarsal 
bones  immediately  below  the  hock  joint,  which,  by  their  freedom  of 
motion  upon  each  other,  enables  the  joint  to  become  more  extended, 
and  the  last  effort  of  the  gastrocnemii  muscles  is  given  with  great 
advantage  of  mechanical  power  from  the  practical  shortening  of  the 
arm  of  the  lever  on  which  they  act,  and  from  the  ability  the  limb 
acquires  of  retaining  its  position  upon  the  ground  for  a  longer  time. 
It  is  a  point  in  some  fast  animals,  but  would  be  considered  a  defect  in 
a  draught  horse. 

Having  given  a  detailed  description  of  the  parts  concerned  in  the 
motion  of  the  posterior  limb,  and  their  action,  I  will  now  endeavor  to 
show  how  the  machine  acts  as  a  whole.  If  the  reader  has  familiarized 
himself  with  the  parts  by  reference  to  the  plates,  while  he  has  followed 
the  description,  he  will  experience  no  difficulty ;  but  if  he  has  not,  it 
would  be  as  well  for  him  to  pass  over  the  rest  of  this  chapter.  The 
analysis  has  no  reference  to  any  particular  gait  or  co-ordination  of  the 
limbs  with  each  other,  but  it  is  confined  to  the  action  of  one  posterior 
limb  alone,  and  it  will  be  found  to  be  the  same  in  all  the  paces,  differ- 
ing only  in  the  degree  of  action  according  to  speed. 

We  will  take  for  our  guide  the  posterior  extremity  as  it  has  just  left 
the  ground,  after  the  act  of  propulsion  is  complete,  and  in  the  medium 
pace,  the  trot. 


TIIK    HOKSM    IN    MOTION.  57 

In  order  to  aid  the  mind  in  understanding  the  actions  of  the  muscles 
upon  their  levers,  the  skeleton  is  mounted  with  movable  joints,  by 
which  means  we  are  enabled  to  adapt  it  to.  every  position  required. 
By  this  means  it  is  a  comparatively  easy  matter  for  one  to  understand 
the  action  throughout  (See  Plates  II.,  XIV.,  XV.) 

Retraction  begins  by  the  relaxation  of  the  gluteus  maximus,  the 
vastus,  semi-membranosus,  and  the  great  adductor.  The  triceps  also 
relaxes,  and  the  tibia  is  free  to  respond  to  the  contraction  of  the  semi- 
tt  nclinosus  lifting  its  lower  extremity.  The  tensor  vagina?,  acting  from 
the  hip  upon  the  knee,  the  psoas  magnus,  iliacus,  and  sartorius  from 
the  inner  and  upper  wall  of  the  pelvis,  with  the  anterior  branch  of  the 
superficial  gluteus  from  the  hip,  all  act  in  concert  to  advance  the  thigh, 
the  knee  becoming  more  flexed  as  it  is  advanced ;  and  with  the  knee, 
or  stifle,  goes  the  hock  joint,  by  the  relaxation  of  the  gastrocnemii  and 
the  mechanical  arrangement  before  described. 

The  flexors  of  the  foot  act  at  the  instant  their  tendons  are  released 
from  the  forced  service  as  ligaments,  and  continue  their  action  until 
the  perpendicular  from  the  centre  of  motion  to  the  ground  is  reached, 
which  marks  the  point  of  greatest  flexion  of  all  the  joints.  The  flexors 
of  the  thigh,  already  mentioned,  maintain  their  tension  to  keep  the 
Imver  extremity  of  the  femur  in  its  advanced  position.  The  semi- 
tendinosus  relaxes,  while  the  triceps  extends  the  tibia  upon  the  femur 
already  well  thrust  forward,  and  the  muscles  of  the  calf,  acting  on  the 
point  of  the  hock,  extend  the  metatarsus  synchronously  with  the  feeble 
action  of  the  extensors  of  the  foot.  The  perforans  and  perforatus  do 
not  take  part  in  this  movement,  as  their  action  would  counteract  that 
of  the  extensor.  In  this  order  the  foot  takes  the  ground,  the  heel 
being  the  first  to  make  the  contact,  and  by  its  elastic  frog  it  is  pecul- 
iarly fitted  to  receive  the  shock.  It  will  be  observed,  by  reference  to 
the  plates,  that  the  bones  of  the  entire  limb  are  at  angles  best  adapted 
to  meet  the  contact  with  the  ground.  The  toe  is  raised  to  avoid  trip- 
ping, and  allow  the  elastic  frogs  of  the  foot  to  make  the  first  contact. 

The  instant  of  contact,  when  the  foot  is  as  far  forward  as  possible 
to  sustain  the  centre  of  gravity,  marks  a  sudden  change.  The  flex- 
ors of  the  thigh,  the  sartorius,  tensor  vaginae  femoris,  iliacus,  and  the 

8 


58  THE    HORSE    IN    MOTION. 

anterior  branch  of  the  superficial  gluteus,  give  way,  while  the  weight 
of  the  body  relieves  the  extensors  of  the  foot.  The  function  of  the 
limb  at  this  time  is  to  support  the  weight  of  the  body  and  prevent  it 
from  pitching  headlong ;  and  to  this  end,  with  the  exception  of  the  few 
small  muscles  just  mentioned,  the  entire  mass  of  the  muscles  of  the 
limb  is  called  into  action ;  and  now  that  the  foot  is  a  fixed  point,  the 
semi-tendinosus  acts  in  unison  with  the  others  to  take  the  weight  of 
the  anterior  half  of  the  body.  This  is  the  use  of  all  the  vast  mass  of 
muscular  power  developed  in  the  haunches  and  long  muscle  of  the  back 
(ilio  spinalis).  In  this  manner  there  is  no  act  of  extension,  further 
than  the  extension  of  the  body  upon  the  thigh ;  it  is  not  until  tht 
centre  of  motion,  or  head  of  the  thigh,  has  passed  over  the  foot  that 
extension  is  possible ;  and  then  the  nearer  to  a  horizontal  the  directior 
of  the  force  applied,  the  more  effective  it  will  be.  When  the  limb  is  per- 
pendicular, the  whole  force  is  employed  in  supporting  weight ;  but  when 
it  is  exerted  upon  the  ground  at  an  angle  of  forty-five  degrees,  one  half 
of  the  force  is  spent  in  supporting  weight,  and  the  other  in  propulsion 
if  it  could  be  exerted  horizontally,  it  is  plain  it  would  be  exclusive!] 
spent  in  propulsion.  From  the  time  when  the  foot  is  planted  ir 
advance,  until  the  leg  has  passed  the  perpendicular,  the  force  is  alsc 
compound,  a  part  being  employed  in  supporting  weight,  and  the  other 
in  resistance  which  must  be  drawn  from  the  momentum  ;  this  last  is 
reduced  to  the  minimum  by  the  gradual  giving  way  of  the  triceps  anc 
gastrocnemii,  and  contraction  of  the  great  propellers  of  the  hauncl 
especially  the  vastus,  which  forces  the  trunk  over  the  supporting  liml 
The  act  of  propulsion  by  the  vastus  begins  from  the  moment  that  the 
hind  foot  takes  the  ground  and  its  contraction  begins.  The  effect  of 
the  contraction  of  this  muscle  is  to  shorten  the  distance  between  its 
two  extremities  ;  one  of  these  extremities  is  attached  to  the  lower 
end  of  the  femur  and  the  other  to  the  spines  of  the  sacrum  behind 
the  croup,  but  the  course  of  the  muscle  is  not  direct  (see  Plate  V.), 
being  deflected  at  the  head  of  the  femur,  and  most  so  when  the 
foot  first  reaches  the  ground.  At  that  time  it  presses  with  most 
force  against  the  articulation  pressing  it  forward,  so  that  it  extends 
the  trunk  upon  the  limb  and  forces  it  forward  in  the  same  act. 


THE    HORSE    IN    MOTION.  59 

After  passing  the  perpendicular,  and  the  angles  of  the  extremity  are 
increased,  the  semi-tendinosus  ceases  to  act,  and  the  extension  is  con- 
tinued by  the  vastus,  gluteus,  triceps,  and  muscles  of  the  calf,  to  the 
end  of  the  stride.  In  the  flexion  of  the  limb  that  takes  place  as  it 
shortens  in  order  to  give  uniform  support,  and  not  be  itself  crushed, 
the  flexion  is  effected  by  the  weight  borne,  in  which  the  flexors  proper 
bear  no  part ;  their  action  could  have  no  other  effect  than  to  bring  the 
body  to  the  ground,  but  it  is  effected  by  the  gradual  giving  way  of  the 
triceps  and  the  suspensory  ligament. 

It  will  be  seen  that  but  a  small  part  of  the  immense  power  of  the 
extensors,  or  propellers  of  the  posterior  extremity,  is  spent  in  the  act 
of  propulsion,  even  when  the  animal  is  in  full  motion,  but  in  supporting 
weight;  and  as  the  extension  of  the  leg  increases  and  the  burden  is 
assumed  by  another  limb,  it  is  the  better  enabled  to  exert  its  propelling 
power.  As  the  limbs  are  successively  relieved  of  that  duty  by  their 
alternates,  they  are  in  better  position  to  exercise  their  functions  as 
propellers. 

This  analysis  of  the  mechanism  of  the  posterior  extremity  will  be- 
come of  importance  when  we  come  to  apply  it  to  the  run  or  greatest 
speed  of  the  horse.  The  reader  who  has  not  had  the  patience  to  fol- 
low us  through  the  study  to  the  end  of  this  chapter  will  not  be  able 
to  master  the  next,  and  we  would  advise  him  to  pass  it  over,  and  take 
up  the  fifth  chapter,  where  we  will  endeavor  to  apply  the  demonstra- 
tions contained  in  these  two ;  but  such  must  take  the  facts  on  which 
the  theory  of  motion  is  based  for  granted. 


CHAPTER   IV. 


THE   COMPARISON  OF  THE  ANTERIOR   EXTREMITY  TO  THE   SPOKES  OF  A  WHEEL  CON- 
SIDERED. —  ITS  THREE   CHARACTERS  OF  CRUTCH,  PASSIVE  TOOL,  AND  ACTIVE  AU- 
TOMATON. —  THE   GREAT   SERRATUS.  —  ITS   DOUBLE   CHARACTER   OF  TENDON  AM 
MUSCLE.  —  CENTRE  OF  MOTION.  —  THE  TRAPESIUS  AND  YELLOW  CORD.  —  LEVATOH 
ANGULI  SCAPULAE.  —  TRACHELO  SUBSCAPULARIS,  ITS  FUNCTION  HITHERTO  UNK\O\V> 
THE    GREAT    DORSAL  AND    PECTORAL  AS   PROPELLERS.  —  THE   MASTOIDO  HUME 
RALIS  AS  AN  EXTENSOR.  —  THE   MUSCLES  OF  THE  SHOULDER-BLADE.  —  THE  P 
OF   MUSCLES   THAT   FLEX   THE   SHOULDER.  —  THE   FUNCTION   OF   THE   TRICEPS 
RESISTING    THE    FALL    OF    THE    BODY    AND    IN    LOCOMOTION.  —  FUNCTION    OF    THE 
FLEXORS  OF  THE  FOREARM.  —  HIGH  ACTION.  —  OBSTACLES  TO  A  FULL  UNDERSTAND 
ING  OF  THE  FUNCTIONS  OF  THE  LOCOMOTIVE   MUSCLES   REMOVED  BY  THE  CAM 
—  ANALYSIS   OF  THE   MOVEMENTS    OF    THE  ANTERIOR    EXTREMITY.  —  MECHANICS 
POINTS   DESIRABLE   IN   A   HORSE   FOR   SPEED  OR   STRENGTH.  —  LOW   CENTRES    OF 
MOTION.  —  LONG  LEVERS.  —  COMPARISON  BETWEEN  THE  ANTERIOR  AND   POSTERIOR 
EXTREMITIES.  —  WHY  QUADRUPEDS  RISE  FROM   RECUMBENT   POSITIONS  WITH  DIFF 
CULTY.  —  WHY   BOXERS   AND    OTHERS   LIABLE   TO    BE   PLACED   SUDDENLY  ON 
DEFENCE  HAVE  THEIR  LIMBS  SEMI-FLEXED.  —  ELEMENTS  OF  SPEED. 


THE  anterior  extremity  furnishes  a  subject  for  the  study  of  anirm 
mechanics  of  more  interest  even  than  that  which  has  demanded  our 
attention  in  the  preceding  chapters. 

There  appear  at  first  sight  greater  difficulties  in  the  way 
human  ingenuity  in  the  application  of  mechanical  power  for  propul 
sion  to  the  anterior  part  of  the  trunk.  The  mind  is  led  by  the  simili- 
tudes of  comparative  anatomy,  and  the  popular  hypothesis  of  evolu- 
tion from  one  common  parentage,  to  look  upon  the  anterior  extrem- 
ities as  limbs  in  progress  of  development  into  arms  or  tool-makers. 
The  mind  jumps,  like  the  kangaroo,  from  the  marsupials  to  the  mon- 
keys, to  the  orang-outang,  and  then  to  man  by  such  easy  leaps  that 
it  is  difficult  to  persuade  one  that  he  has  advanced  to  his  opinions 


without  substantial 


grounds. 


To  these  causes  must  be  ascribed  th 


TIIK    HORSE    IN    MOTION.  6l 

universal  opinion  of  writers  on  the  horse  that  the  fore  legs  are 
merely  supporters;  and  the  latest  and  standard  authority  on  the 
horse,  in  England, compares  them  to  the  spokes  of  a  wheel,  and  asserts 
that  their  only  functions  are  to  support  the  centre  of  gravity  and  keep 
out  of  the  way  of  the  propellers,  the  hind  legs.  It  will  be  apparent 
to  the  reader  before  the  conclusion  of  this  chapter,  if  it  is  not  ,so 
already,  that  each  limb  is  required  to  support  the  body  and  act  as 
propeller  in  turn,  and  that  the  anterior  one  does  more  than  its  share 
of  both  offices.* 

It  will  be  shown,  when  we  come  to  analyze  the  fastest  pace  of 
the  horse,  that  the  strongest  propulsive  force  of  either  of  the  legs 
is  given  with  the  anterior  one  in  each  stride ;  indeed,  it  is  so  strong 
as  to  raise  the  centre  of  gravity  several  inches  above  the  horizontal 
line  of  its  motion.  As  the  case  now  stands  between  the  anterior 
and  posterior  extremities,  they  may  be  compared  to  a  peasant  and 
his  wife  in  certain  foreign  lands,  in  which  the  latter  is  required  to 
share  equally  with  her  husband  in  all  his  labors  and  also  to  bear 
burdens  which  he  cannot  share  with  her. 

The  beautiful  contrivances  by  means  of  which  the  anterior  limb 
is  enabled  to  support  weight  as  a  crutch,  to  be  acted  upon  as  a 
passive  instrument  in  propulsion,  and  at  the  same  time  to  consti- 
tute an  autonomy  of  its  own,  independent  of  both  the  others,  for  the 
accomplishment  of  the  same  general  result,  cannot  fail  to  excite  the 
most  profound  admiration,  and  wonder  that  its  mechanism  has  not 
been  better  understood. 

On  reference  to  Plate  IV.,  s,  one  will  see  the  posterior  half  of 
the  great  serratus  brought  into  view  by  the  removal  of  the  superficial 
muscles  that  hide  it  in  Plate  III.  It  is  so  called  because  its  lower 
border  is  serrated  or  notched,  the  lower  attachments  being  to  the 
first  eight  ribs ;  the  anterior  half  of  the  muscle  is  concealed  by  the 
shoulder.  This  muscle  is  fan-shaped,  its  fibres  converging  upward 

*  Mr.  Walsh  (Stonehenge)  gives  the  authority  of  M.  Baucher  for  the  statement  that 
the  weight  borne  by  the  anterior  and  posterior  extremities,  as  determined  by  placing  them 
upon  different  weighing-machines,  was  as  210  for  the  former  to  174  for  the  latter,  the  total 
weight  of  the  horse  being  384  kilogrammes. 


62 


THE    HORSE    IN    MOTION. 


to  a  common  centre  on  the  inner  face  of  the  upper  border  of  the 
shoulder-blade,  or  scapula,  as  seen  in   Plate  XL,  .$•,  s. 

When  this  muscle  is  recently  exposed  it  presents  delicate  nacre- 
ous tints  rivalling  pearl.  The  artist  has  suggested  them  only  in  his 
drawing.  This  pearly  coat  of  the  muscle  is  tendinous  in  its  struc- 
ture, and  extends  over  the  whole  exterior  surface  of  the  great  serra- 
tus.  These  tendinous  fibres  extend  throughout  the  muscle,  but  are 
in  greater  proportion  near  the  centre  or  long  axis  (Plate  XI.,  a). 
These  tendinous  fibres,  concentrated  at  a,  mav  be  considered  the 
centre  of  motion  for  the  whole  limb  when  supporting  the  weight  of 
the  body,  whether  acting  alone,  or  in  conjunction  with  one  or  more 
of  the  other  limbs,  and  whatever  may  be  the  direction  of  its  axis 
with  reference  to  the  trunk ;  but  this  centre  of  motion  must  not  be 
confounded  with  the  centres  of  motion  existing  in  the  joints ;  it 
holds  a  corresponding  position  with  the  "  whirlbone,"  or  hip  joint 
of  the  posterior  extremity.  This  intermixture  of  muscular  and 
tendinous  fibres  existing  in  this  muscle  is  found  in  others,  as  the 
deep  gluteus  described  in  the  last  chapter,  enabling  it  to  perform 
the  functions  of  both  muscle  and  ligament.  The  tendinous  fibres 
which  are  in  the  greatest  proportion  in  the  long  axis,  when  put 
to  their  tension  absolutely  limit  elongation  to  that  degree,  and  ar 
useful  when  the  animal  is  standing ;  as  these  tissues  are  incapable 
of  fatigue,  so  he  has  no  occasion  to  rest  them.  With  the  aid  of 
another  muscle,  which  we  shall  describe  further  on,  having  the  same 
characteristic  construction  as  the  serratus,  the  horse  is  enabled  to 
stand  in  his  stall  all  day  without  resting  either  of  his  fore  legs ; 
while  in  the  hind  leg  the  labor  falls  upon  the  triceps  (Plate  IV.,  /), 
of  pure  muscular  fibre,  and  he  will  be  observed  to  rest  his  hind  legs 
alternately.  (See  page  50.) 

The  muscular  fibres  of  the  serratus  are  most  abundant  at  the 
anterior  and  posterior  borders.  The  former  aid  in  preventing  shock 
when  the  foot  first  takes  the  ground,  and  the  latter  in  giving  the 
final  propulsive  effort  when  it  leaves  it ;  and  by  their  joint  action 
they  relax  the  tendinous  fibres,  or  bands,  which,  being  passive,  have 
no  such  power  in  themselves. 


XI. 


n 


--77 


INTI    - 


TIIK    1IORSK    IN    MOTION'.  63 

The  centre  of  motion  in  the  anterior  extremity  may,  in  its 
mechanical  function,  be  considered  as  a  joint,  and  the  only  kind  of 
joint  possible  in  that  position;  were  it  constructed  like  the  corre- 
sponding joint  in  the  posterior  extremity,  it  would  be  inevitably 
broken  by  the  contact  with  the  ground,  thrown  out  as  it  is  in 
advance  of  the  centre  of  gravity.  For  the  same  reason  it  is  not 
provided  with  a  collar-bone,  or  clavicle,  as  in  man  and  the  anthro- 
poid animals,  in  whom  that  bone  fixes  the  shoulder  and  makes  it 
the  centre  of  motion  for  the  limb. 

On  reference  to  Plate  IV.,  s,  the  great  serratus  will  be  seen  as  a 
fan-shaped  muscle  which  has  its  lower  attachments  spread  out  over  the 
first  eight  ribs.  From  the  attachment  to  the  different  ribs  its  lower 
border  is  like  a  saw,  from  which  its  name,  "serratus."  The  artist 
has  vainly  attempted  to  represent  the  nacreous  color,  in  which  it  vies 
with  the  mother-of-pearl.  This  is  the  tendinous  covering  to  the 
muscle,  and  it  is  much  intermingled  with  tendinous  fibres,  which 
limit  elongation  and  take  the  strain  from  the  muscular  fibres  when 
their  contraction  is  not  called  for.  The  upper  attachment  of  this 
muscle  is  on  the  inner  face  of  the  scapula,  or  shoulder-blade  (Plate 
XI.,  (?),  below  the  cartilaginous  border,  with  the  dark  line  mark- 
ing the  boundary  between  it  and  other  muscles.  In  the  centre 
are  seen  the  gray  fibres  of  tendon,  which  are  continuous  below, 
and  enable  the  animal  to  rest  the  muscular  fibres  and  limit  their 
elongation.  The  space  covered  on  the  inner  face  of  the  scapula  is 
nine  inches  in  its  greatest  measurement  by  two  in  its  least. 

The  space  below  the  section  of  the  serratus,  as  seen  in  s,  s, 
Plate  XL,  and  between  that  muscle  and  those  of  the  inner  face  of  the 
shoulder-blade,  is  lined  with  loose  cellular  tissue,  which,  while  it  con- 
nects the  opposing  surfaces,  allows  of  unrestricted  motion  upon  the 
centre,  a,  and  prevents  friction.  The  body  in  a  standing  position 
rests  the  weight  of  the  anterior  half  upon  these  serratus  muscles  as 
upon  a  sling  to  which  the  anterior  extremities  correspond  to  crutches. 
.  But  when  the  foot  of  one  of  these  limbs  is  off  the  ground  the 
serratus  is  relaxed,  and  the  limb  would  drop  but  for  another  set  of 
muscles,  which,  though  feeble,  are  sufficient  for  the  purpose  which 


64  THE    HORSE    IN    MOTION. 

they  serve.  This  is  the  special  function  of  the  trapezius  (g,  g, 
Plate  III.).  It  is  so  perfectly  represented  in  the  plate  that  it  requires 
but  little  description.  It  is  divided  into  two  parts  by  the  spine  of 
the  scapula  (see  Plate  II.),  into  which  both  divisions  are  inserted 
along  with  a  band  of  the  ligament  of  the  neck,  which  seems  to  be 
sent  off  for  the  purpose  of  aiding  with  its  passive  force  the  trape- 
zius in  holding  the  limb  to  its  place.  The  upper  insertions  or  origins 
of  both  divisions  are  in  the  same  ligament  of  the  neck,  or  yellow  cord, 
as  it  is  well  called  by  hippo-anatomists.  This  cord  is  distinguished 
not  only  by  its  color  but  by  its  elasticity  from  all  other  ligaments. 
It  seems  to  be,  indeed,  a  special  contrivance  to  afford  means  for  the 
attachment  of  important  muscles  when  the  spines  of  the  vertebra 
are  too  remote  to  afford  it.  It  extends  from  the  head  to  the  strong 
spines  of  the  dorsal  vertebra,  where  it  becomes  merged  into  ordinary 
ligament.  It  may  be  that  the  branch  of  this  cord  that  is  inserted 
into  the  spine  of  the  scapula  is  itself  sufficient  to  support  the  weight 
of  the  anterior  limb,  and  that  the  muscle  under  consideration  is  used, 
the  two  parts  acting  alternately,  to  aid  in  locomotion,  exerting  their 
forcj  at  the  upper  or  cartilaginous  extremity  of  the  scapula  and  above 
the  centre  of  motion  or  attachment  of  the  serratus ;  but  however  that 
may  be,  its  aid  in  locomotion  cannot  be  great,  as  its  entire  weight 
does  not  exceed  two  ounces.  Its  thickness  does  not  vary  much  from 
half  an  inch.  It  is  separated  from  the  skin  only  by  the  general 
aponeurosis,  or  fibrous  covering  described  in  a  former  chapter,  and 
which  has  been  dissected  away  from  the  whole  body  in  the  subject 
of  the  drawings. 

When  the  trapezius  is  removed,  the  rhomboideus  is  brought  into 
view.  This  muscle  is  so  named  from  the  corresponding  muscle  in 
man,  in  whom  it  is  in  the  form  of  a  rhomboid ;  and  if  the  name  were 
limited  to  the  muscle  so  far  as  it  corresponds  to  that  in  man  there 
could  be  no  objection  to  it,  but  since  Cuvier's  time  it  has  been  made 
to  embrace  another  muscle,  the  levator  anguli  scapula  (Plate  IV.,  /) 
To  this  union  in  the  horse  there  can  be  no  objection,  anatomically 
or  mechanically;  but  when  so  united  they  are  no  more  like  a  rhom- 
boid than  a  tent-pin,  and  the  name  of  levator  anguli  scapulae  should 


THE    HORSE    IN    MOTION.  65 

have  been  applied  to  the  united  muscles,  if  either;  but  the  worst 
part  of  the  history  is  that  the  name  of  levator  anguli  scapula?  was 
applied  to  another  muscle,  the  trachclo  subscapularis  (Plate  IV.,  g,  g). 
No  name  could  be  more  inappropriate  than  this;  in  no  way,  directly 
or  indirectly,  can  it  be  said  to  lift  the  angle  of  the  scapula,  as  may  be 
seen  by  reference  to  the  plate.  The  function  of  this  last-named  mus- 
cle has,  so  far  as  I  know,  never  been  understood  until  now,  and  will 
be  explained  further  on.  But  this  furnishes  another  example  of  the 
confusion  arising  from  hippo-anatomists  being  misled  by  human  anat- 
omy. The  levator  anguli  scapulas  is  quite  distinct  from  the  rhom- 
boideus  in  man,  having  its  origin  in  the  transverse  processes  of  the 
vertebra  of  the  neck,  while  in  the  horse  its  origin  is  in  the  spinous 
processes  of  the  vertebra,  as  far  back  as  the  withers  and  along  the 
yellow  cord.  (See  Plate  IV.)  In  man,  its  name,  lifter  of  the  angle 
of  the  scapula,  is  good,  for  that  expresses  its  function ;  in  man, 
however,  it  is  no  locomotive  organ,  but  even  more  necessary  to 
the  complicated  movements  his  superior  extremities  are  required  to 
perform. 

From  the  necessity  which  exists,  for  the  reasons  given,  of  restoring 
the  old  name  to  the  trachelo  subscapularis,  the  restoration  of  the 
name  levator  anguli  scapulae  to  its  old  association  becomes  necessary, 
if  it  is  not  to  be  abandoned  altogether.  In  order  to  make  intelli- 
gible a  description  of  the  mechanical  action,  there  is  need  of  definite 
terms,  and  we  will  apply  the  name  levator  anguli  scapulae  to  include 
the  rhomboideus  as  well. 

The  contraction  of  its  fibres  does  not  take  place  until  the  leg  is 
extended  and  the  foot  rests  upon  the  ground ;  it  then  acts  to  draw 
forward  the  tipper  or  short  end  of  the  whole  extremity  as  a  lever 
with  its  fulcrum  on  the  ground  and  its  weight  at  the  centre  of  motion. 
The  course  of  its  fibres  is  accurately  drawn  in  the  plate,  the  limb 
being  in  its  normal  position.  Its  posterior  fibres  are  few,  but  as  it 
extends  forward  they  become  numerous  and  more  powerful.  Their 
insertion  is  into  the  inner  border  of  the  cartilage  (Plates  IV.  and  XL, 
«,  «, ;/);  at  the  anterior  border,  »',  is  the  insertion  of  the  muscle  known 
before  the  time  of  Cuvier  as  the  levator  anguli  scapulae ;  they  form  a 

9 


66  THE   HORSE    IN    MOTION. 

considerable  mass,  and  join  on  to  the  serratus,  s,  so  nearly  in  the 
line  of  the  centre  of  motion  that  it  may  be  that  they  act  in  con- 
junction with  the  trachelo  subscapularis,  whose  insertion  is  at  g, 
Plate  XI. 

The  last-named  muscle  is  well  exposed  in  Plate  IV.,  g,  g.  As 
there  seen,  it  is  triangular.  It  arises  from  the  transverse  processes  of 
the  last  six  cervical  vertebra,  and  its  fibres  converge  to  their  inser- 
tion on  the  inner  face  of  the  scapula,  in  front  of  the  insertion  of  the 
serratus,  or  centre  of  motion.  Its  muscular  fibres  are  in  little  fasci- 
culce,  or  bundles,  separated  by  interstitial  fibrous  or  cellular  tissue, 
to  admit  of  great  freedom  of  motion  upon  each  other  in  the  extreme 
vertical  flexions  of  the  neck  while  grazing.  It  is  a  powerful  muscle, 
its  weight  being  three  and  a  half  pounds ;  but  its  action  has  not  been 
comprehended,  its  fibres  being  nearly  horizontal  on  an  average,  or  a 
little  upward,  and  their  insertion  on  a  line  with  the  centre  of  motion ; 
it  can  have  no  active  agency  in  locomotion,  though  with  the  joint 
action  of  the  levator  anguli  scapulae  it  may  move  the  upper  end  of  the 
scapula  forward,  as  far  as  permitted  by  the  tendinous  fibres  of  the 
serratus  and  the  branch  from  the  yellow  cord ;  but  that  cannot  be 
much.  Until  the  theory  of  quadrupedal  motion  was  understood  its 
function  may  well  have  been  overlooked.  It  is  now  clear.  Its  attach- 
ment being  on  a  line  with  the  centre  of  motion  and  directly  upon  a 
fixed  point,  it  cannot  be  supposed  to  aid  in  the  motion  of  the  scapula 
about  that  point;  but  when  the  animal  is  running,  and  the  fore  leg 
is  thrown  forward  and  takes  the  ground,  it  is  required  alone  to 
receive  the  weight  of  the  whole  body  or  be  itself  crushed  by  its 
momentum.  This  will  be  resumed  after  the  action  of  the  triceps 
brachii  at  the  same  instant  is  shown.  It  is  sufficient  for  the  present 
that  the  action  of  this  muscle  abstractly  be  understood  and  remem- 
bered. Its  general  appearance  is  so  like  the  muscle  above  it,  the 
scale nus  (m,  m,  m),  having  similar  origins  along  the  cervical  ver- 
tebra nearer  the  head,  and  its  insertions  into  the  spines  of  the  dorsal 
vertebra  (hidden  in  the  plate  by  the  overlaying  levator  anguli  scap- 
ulae), that  it  is  apt  to  be  confounded  with  it;  but  the  scalenus  is 
not  a  locomotive  muscle,  its  function  being  to  raise  the  head  when 


THE    HORSE    IN    MOTION.  67 

the  pair  act  unitedly,  and  to  bend  the  neck  laterally  when  each 
muscle  acts  separately. 

\Ve  have  shown  how  the  anterior  extremity  is  used  as  a  supporter 
to  the  trunk,  or  crutch,  and  how  it  is  itself  supported  in  its  position 
when  not  so  acting.  The  mechanical  principles  involved  are  very 
simple.  The  method  in  which  mechanical  power  is  applied  to  the 
same  limb  as  a  lever  in  locomotion  will  be  found  to  be  no  less  so,  and 
if  the  contrivance  does  not  display  as  great  ingenuity  as  some  parts 
of  the  locomotive  organs,  it  is  because  there  was  no  occasion  for  such 
display :  it  has  the  merit,  at  least,  of  being  very  primitive. 

\Yhile  there  is  no  bony  connection  between  -the  anterior  extremity 
of  the  horse  and  its  trunk,  therefore  no  fixed  point  of  resistance 
and  reaction,  as  in  the  posterior  extremities,  the  centre  of  motion  is 
attained  equally  well,  and  it  is  difficult  to  conceive  how  it  could  serve 
its  different  relations  to  the  trunk  any  better.  The  centre  of  motion 
in  the  anterior  extremity  is  in  the  scapula,  as  high  as  a  bony  base  could 
be  reached.  This,  if  not  anatomically  so,  is  mechanically  a  joint,  and 
corresponds  to  the  hip  joint  of  the  posterior  extremity,  the  shoulder  to 
the  stifle,  and  the  elbow  to  the  hock.  In  this  view,  there  is  no  reversed 
order  in  the  joints,  as  has  been  stated,  but  the  same  mechanical  relation. 
The  freedom  of  motion  at  its  centre  in  the  limb  is  less  than  in  the 
corresponding  joint  in  the  posterior  extremity,  but  there  is  all  that 
is  required ;  it  is  placed  considerably  higher  than  in  the  latter,  in 
order  that  more  motion  should  not  be  required  ;  and  the  restriction 
at  that  point  is  compensated  for  by  the  superior  flexibility  of  the  lower 
joints.  The  total  result  is  that  the  stride  of  one  limb  is  just  equal  to 
that  of  the  other. 

The  limb,  acting  as  a  lever  of  the  third  order,  having  its  centre  of 
motion  as  high  as  possible,  should  have  the  power  to  move  it  applied  as 
low  down  as  possible,  within  the  periphery  of  the  body ;  but  the  farther 
from  the  fulcrum,  or  centre  of  motion,  the  power  is  applied,  the  greater 
will  be  the  space  moved  over,  and,  consequently,  the  longer  must  be 
the  fibres  of  the  muscle.*  This  requisite  is  furnished  by  the  great 
dorsal  (Plate  III.,  d,  d),  which  has  for  its  base  the  spines  of  the  last 

•  See  page  31. 


68  THE   HORSE   IN   MOTION. 

fifteen  dorsal  and  the  lumbar  vertebra.  Though  spread  over  so  much 
space,  the  muscular  tissue  is  not  correspondingly  extensive.  The  pur- 
pose was  to  gain  advantage  of  position  as  far  back  as  possible  to  give 
the  most  direct  action  in  the  line  of  motion  to  be  produced.  As  the 
fibres  of  its  thin  tendon  (Plate  III.,  /,/")  converge  forward  and  down- 
ward, they  become  more  muscular,  and  most  so  just  behind  the  scapula, 
which  is  covered  at  its  posterior  angle  by  it,  and  it  is  covered  in  turn 
in  the  same  region  by  the  dorsal  division  of  the  trapezius,  g ;  after  pass- 
ing beneath  the  muscles  of  the  shoulder  (as  seen  in  Plate  XL,  d,)  its 
fibres  again  change  to  a  thin,  flat  tendon,  which  unites  with  the  tendon 
of  the  muscle,  f,  and  is  inserted  with  it  into  the  internal  tubercle  of  the 
humerus,  about  one  third  of  the  way  from  the  shoulder  to  the  elbow. 
If  this  muscle  acted  when  the  foot  is  off  the  ground,  it  is  plain  that  it 
would  flex  the  shoulder;  but  its  function  as  a  propeller  is  called  into 
play  when  the  foot  is  the  fixed  point,  and  the  limb  is  supporting  the 
weight  of  the  body,  and  its  articulations  are  all  set.  Under  such  con- 
ditions it  forces  the  body  forward  over  the  foot;  but  its  power  as  a  pro- 
peller is  second  to  that  of  the  great  pectoral  (Plate  III.,/,  p).  The 
limits  of  this  muscle  are  a  little  in  doubt.  It  is  represented  in  the 
plate  with  the  boundaries  as  given  by  Chauveau,  but  it  is  confounded 
so  closely  with  the  superficial  muscle  of  the  skin  (paniculus  carnosus) 
on  its  upper  border  that  it  is  difficult  to  separate  them.  For  our 
purpose,  it  is  sufficiently  shown  in  the  plate,  extending  from  the  tenth 
rib  over  the  thorax,  covering  the  serratus  magnus  as  high  as  the  lower 
border  of  the  great  dorsal,  and  as  low  as  the  middle  of  the  thorax, 
where  it  unites  with  its  fellow  of  the  opposite  side.  Its  fibres  con- 
verge as  they  are  directed  forward,  and  form  a  mass  of  muscle  between 
the  arm  and  thorax  so  great  as  to  be  second  in  power  to  no  other  loco- 
motive muscle  in  the  body.  Its  insertion  is  into  the  inner  tubercle 
of  the  head  of  the  humerus,  as  seen  at  p,  Plate  XI.,  as  near  to  the 
shoulder  joint  as  possible.  The  great  dorsal  may  perform  two  func- 
tions, flexion  or  propulsion,  as  mentioned.  The  muscle  now  under 
consideration  has  but  one.  Acting  directly  upon  the  angle  of  the 
shoulder,  there  is  no  loss  of  its  immense  power  by  indirect  force,  and 
from  the  moment  that  the  foot  touches  the  ground,  its  power  is  felt  in 


THE    HORSE    IN    MOTION.  69 

forcing  the  body  over  it.  As  there  is  no  loss  of  force  in  indirect 
action,  so  there  is  none  spent  in  adduction  or  abduction,  or  in  sup- 
porting weight ;  that  office  is  performed  by  the  muscles  of  the  limb 
acting  automatically,  and  the  effect  of  its  traction  upon  the  shoulder 
is  to  support  it  and  prevent  it  from  giving  way  while  the  limb  is 
playing  its  independent  part  in  sustaining  the  superimposed  weight 
of  the  body. 

There  seems  no  room  for  a  doubt  that  the  conjoined  action  of  the  two 
sets  of  muscles  last  described  is  the  most  powerful  propelling  force  in 
the  whole  locomotive  organism  of  the  horse.  To  make  this  apparatus 
complete,  there  was  necessary  some  force  to  return  the  limb  to  its  posi- 
tion forward  when  the  act  of  propulsion  was  completed.  This  force  is 
found  in  two  sets  of  muscles,  the  masloido  humeralis  and  the  superficial 
pectoral;  the  former  has  its  fixed  insertion  at  the  mastoid  process  of  the 
temporal  bone,  or  base  of  the  skull,  behind  the  ear,  and  to  the  first  four 
cervical  vertebra.*  It  is  shown  in  Plate  III.,  m,  m,  m,  passing  downward 
and  backward  along  the  whole  length  of  the  neck  and  over  the  point 
of  the  shoulder,  enveloping  it,  and  is  inserted  at  the  humerus,  about 
half-way  from  its  two  extremities.  (See  Plate  IV.,  i,  where  the  muscle 
has  been  cut  away  from  its  tendon  of  insertion.  It  is  also  severed  at/, 
leaving  only  its  upper  portion  in  situ.)  It  is  six  inches  in  width  where 
it  envelopes  the  shoulder  joint,  and  an  inch  in  thickness,  and  gives 
off,  about  thirteen  inches  above  its  insertion,  a  branch  to  be  inserted 
at  the  anterior  border  of  the  sternum,  or  breast-bone.  This  branch, 
which  could  not  be  well  shown  in  the  drawing,  is  known  to  anatomists 
as  the  cuticularis  colli.  There  does  not  appear  to  be  any  occasion  to 
consider  it  a  distinct  muscle ;  its  fibres  are  interwoven  with  those  of 
the  muscle  under  consideration ;  its  function  is  to  aid  that  muscle, 
and  fix  it  in  its  position  over  the  shoulder  joint.  Though  so  thin, 
the  weight  of  the  mastoido  humeralis  is  not  less  than  five  pounds. 
To  give  effect  to  this  muscle,-  it  is  necessary  that  its  base,  the  head, 
should  be  fixed.  This  is  effected  by  the  complexus,  and  its  allies  of 

'  This  relation  is  not  well  shown  in  the  drawings,  owing  to  displacement,  caused  by  the 
cord  used  in  suspending  the  subject ;  the  artist  drew  the  parts  as  he  saw  them,  and  the 
inaccuracy  was  overlooked  until  too  late  to  be  corrected. 


•JQ  THE   HORSE   IN   MOTION. 

the  neck.  From  this  it  follows  that  the  horse,  in  speeding,  should  be 
allowed  to  follow  its  instinct  in  fixing  the  position  of  the  head.  The 
ally  of  this  muscle  is  the  superficial  pectoral,  which  has  its  insertion 
on  the  anterior  extremity  and  lower  margin  of  the  sternum,  or  breast- 
bone. The  course  of  its  fibres  is  backward,  downward,  and  outward  ; 
they  divide  into  two  branches :  one  is  inserted  into  the  anterior  ridge 
of  the  humerus,  along  with  the  mastoido  humeralis ;  the  other  is 
spread  out  on  the  fascia  of  the  inner  face  of  the  leg.  The  action  of 
this  muscle  is  to  carry  the  whole  limb  forward,  in  common  with  the 
last  described,  and  at  the  same  time  to  adduct  it  to  counteract  the 
abduction  of  that  muscle. 

The  action  of  these  two  sets  of  muscles  is  so  unlike  any  other  that 
it  is  not  readily  understood.  Let  us  suppose  a  man  propelling  a  boat 
through  the  water  by  means  of  an  oar,  and  the  handle  end  of  the  oar 
made  fast  to  the  side  of  the  boat  opposite  to  that  on  which  he  is 
seated,  but  free  to  move  about  a  pin  ;  then  let  the  man  remove  the 
rowlock  from  its  place  and  substitute  for  it  his  hands ;  next  make  fast 
the  blade  of  the  oar  in  the  water,  and  the  man  shall  then  apply  his 
strength  to  the  oar :  the  boat  will  move.  Now,  if  this  illustration  be 
modified  so  that  the  oar  shall  be  vertical,  and  the  blade  of  the  oar  be  fixed 
to  the  bottom,  and  the  handle  to  a  fixture  above  the  man's  head,  the 
similitude  will  be  complete.  Of  course  the  nearer  the  power  is  applied 
to  the  foot,  or  fulcrum,  the  faster  the  upper  end  will  move,  but  the 
greater  must  be  the  expenditure  of  power.  There  is  another  muscle, 
acting  from  without  upon  the  shoulder,  whose  office  has  been  doubtful, 
the  small  pectoral.  It  arises  from  the  keel  of  the  sternum,  or  breast- 
bone, and  passing  between  the  shoulder  and  the  neck,  fills  the  angular 
space  in  front  of  the  scapula.  It  is  thick  below,  where  it  is  turned  over 
the  breast,  and  becomes  smaller  as  it  is  reflected  on  the  scapula,  tri- 
angular in  form,  to  fit  the  space  it  fills,  and  is  the  muscle  against  which 
the  collar  rests ;  this  is  a  muscle  of  considerable  power,  being  two  and 
a  half  pounds  in  weight.  It  is  attached  to  the  muscles  of  the  scapula 
by  strong  cellular  tissue,  and  to  the  strong  aponeurosis  that  covers  it. 
Besides  being  an  element  of  beauty,  by  giving  graceful  contour  to  the 
parts,  it  seems  to  have  no  other  function  than  to  pull  forward  the  whole 


THE    HORSE    IN    MOTION.  71 

limb,  rendering  tense  the  tissues  connecting  it  with  the  trunk,  and  by 
so  doing  extending  the  limb  to  enable  it  to  take  the  ground  farther  in 
advance,  and  leads  us  to  infer  how  great  importance  was  attached  by 
the  Master  Mechanic  to  utilizing  every  available  means  to  enable  the 
fore  foot  to  reach  the  ground  as  far  in  advance  as  possible,  that  no 
time  might  be  lost  in  giving  support  to  the  centre  of  gravity. 

We  have  thus  far  considered  the  anterior  extremity  as  a  passive 
tool  taken  as  a  unit ;  it  remains  to  study  it  as  an  active  automatic 
machine.  It  is  difficult  to  trace  any  analogy  between  the  mechan- 
ism of  the  anterior  and  posterior  extremities  thus  far;  but  in  the 
system  of  levers,  by  the  closing  of  which  the  limb  is  shortened,  and 
in  the  opening  of  which  it  is  lengthened,  we  recognize  the  same 
mechanical  combinations  that  are  employed  for  the  same  purpose  in 
the  posterior  extremity. 

In  Plate  IV.  the  external  view  of  the  shoulder  and  arm  is  given 
showing  its  relation  to  the  trunk  and  that  of  the  muscles  to  each  other. 
The  pearly-colored  upper  border  of  the  scapula,  n,  n,  is  seen  with 
the  levator  anguli  scapulae  still  attached.  This  border,  which  is  car- 
tilaginous, is  not  seen  in  the  prepared  skeleton,  but  a  rough  margin 
to  the  bone  indicates  its  former  connection.  No  muscle  of  the  ante- 
rior extremity,  as  an  automatic  machine,  is  attached  to  this  cartilagi- 
nous border.  It  has  not  sufficient  firmness  to  resist  force  from  below, 
but  its  tenacity  is  sufficient  to  withstand  great  traction,  and  its  flexi- 
bility is  such  as  to  prevent  any  danger  of  fracture  by  force  so  applied. 
The  spine  of  the  scapula  may  be  traced  from  the  cartilage  downward, 
near  the  middle  of  it,  to  which  the  trapezius  and  branch  of  the  yellow 
cord  were  attached.  This  spine  divides  unequally  the  scapula ;  in  front 
of  it  is  the  superspinatus  muscle,  s  s,  whose  terminal  tendons  pass 
over  the  head  of  the  humerus,  or  shoulder,  one  to  be  inserted  into  the 
external  tubercle  on  the  outside,  and  one  third  of  the  distance  from 
the  point  of  the  shoulder  to  the  elbow.  This  is  the  most  consider- 
able division,  and  acts  to  extend  the  humerus  on  the  scapula  and 
rotate  it  outward.  The  other  tendon  is  inserted  near  the  internal 
tuberosity;  it  unites  with  its  fellow  in  extending  the  humerus.  Con- 
sidering this  muscle  mechanically,  it  would  be  proper  to  regard  its 


72  THE    HORSE    IN    MOTION. 

lower  insertions  as  one,  overlaying  the  joint  beneath  the  mastoido 
humeralis,  and  acting  on  the  head  of  the  humerus  as  a  direct  extensor 
of  the  humerus ;  its  weight  is  two  pounds,  and  its  length  seventeen 
inches. 

The  shoulder  joint  is  constructed  on  the  same  principle  as  that 
of  the  hip,  but  the  head  of  the  humerus  is  broader  and  less  convex, 
and  the  cavity  of  the  opposing  articular  surface  of  the  scapula  too 
small  to  lodge  it;  but  it  is  supplemented  by  cartilage  and  ligaments, 
and  held  still  more  strongly  in  its  position  by  the  powerful  tendons 
which  envelop  it.  The  head  of  the  humerus  is  held  in  its  place 
by  the  further  assistance  of  the  atmospheric  pressure  equal  to  one 
hundred  pounds.  Though  freedom  of  motion  is  not  so  great  as  in  the 
corresponding  articulation  in  man,  it  is  much  greater  than  that  of 
the  hip  joint. 

The  two  muscles  that  especially  guard  the  joint  and  prevent  later 
displacement  are :  the  infraspinatus  (i  s),  which  is  attached  to  the  ex- 
ternal surface  of  the  scapula,  and  nearly  fills  the  space  below  its  spine. 
It  is  inserted  into  the  head  of  the  humerus,  at  <?,  directly  opposite  the 
shoulder  joint;  the  other  is  the  subscapularis  ( Plate  XL,  /»),  having 
its  attachment  on  the  inner  surface  of  the  scapula,  and  occupying  the 
whole  face  of  the  bone  below  the  insertion  of  the  serratus,  s,  and 
is  inserted  into  the  inner  side  of  the  head  of  the  humerus,  directl) 
opposite  to  the  insertion  of  the  infraspinatus.  These  two  muscles 
are  of  the  same  power,  each  weighing  two  and  a  half  pounds,  and  of 
the  same  length.  Acting  simultaneously,  they  neither  flex  nor  extend 
the  humerus,  the  abduction  of  the  one  cancelling  the  adduction  of 
the  other,  but  they  are  powerful  braces  to  the  joint. 

There  is  another  pair  of  muscles,  whose  functions  cannot  be  under- 
stood unless  considered  together.  If  the  reader  will  refer  to  any  one 
of  the  silhouettes  of  the  trotting  horse,  and  watch  the  action  of  the 
fore  leg  from  the  time  that  the  foot  leaves  the  ground  until  it  takes  a 
new  position  in  advance,  he  will  perceive  that  all  the  joints  are  flexed 
rapidly  before  the  foot  passes  the  perpendicular.  The  flexion  at  the 
shoulder  is  performed  by  these  two  muscles.  One  is  called,  by  Chauveau, 
the  long  adductor ;  teres  minor,  by  Percivall ;  and  the  scapula  hume- 


THE    MORSE    IN'    MOTION.  73 

ralis,  by  Legh.  The  other  is  called  the  adductor  of  the  arm,  by 
Chauveau  ;  (ors  major,  by  Percivall ;  and  the  great  scapula  humeralis, 
by  Legh.  One  acts  on  the  outer  and  the  other  on  the  inner  aspect  of 
the  humerus,  at  equal  distances  from  the  shoulder  joint,  and  nearly  one 
third  of  the  distance  from  the  articulation ;  one  from  the  outer,  and  the 
other  from  the  inner  surface  of  the  scapula;  and  the  weight  of  each  is 
one  pound,  while  their  length  is  the  same.  They  cannot  be  conceived 
as  acting  independently  of  each  other,  and  it  is  useless  to  consider 
what  their  function  would  be  when  so  acting.  Conjointly  they  are 
neither  adductors  nor  abductors,  but  flexors  of  the  shoulder.  While 
the  bone  is  thus  flexed,  the  limb  is  brought  forward  by  the  mastoido 
humeralis,  which  is  inserted  into  the  same  ridge  as  the  external  of 
these  two  muscles. 

When  the  time  comes  for  a  thorough  revision  of  the  names  of  the 
muscles  of  the  horse  (and  that  time  must  come  soon,  for  it  is  now  con- 
fusion worse  confounded),  it  is  to  be  hoped  they  will  be  determined  by 
their  mechanical  action  without  reference  to  the  action  of  corresponding 
muscles  in  man.  The  camera  has  now  made  the  task  comparatively 
easy.  When  that  time  comes,  these  muscles  should  be  known  as  the 
flexors  of  the  shoulder,  internal  and  external. 

There  are  two  flexors  of  the  forearm.  The  flexor  brachii  is  a  short 
tendinous  muscle,  originating  from  the  lower  anterior  extremity  of  the 
scapula,  just  above  the  centre  of  the  shoulder  joint,  by  a  strong  tendon, 
which  is  developed  into  a  patella-formed  cartilage,  moulded  to  the 
double  groove  on  the  anterior  angle  of  the  humerus,  over  which  it 
glides  as  a  synovial  articulation,  or  a  pulley,  in  the  same  manner  as  the 
patella  of  the  stifle  joint,  the  grooves  being  deep  so  as  to  prevent 
lateral  displacement  in  extreme  flexion.  Below  the  shoulder  it  forms 
a  cylindrical  muscle  ten  inches  long.  Its  muscular  fibres  are  inter- 
mingled with  tendinous  bands,  by  which  its  elongation  is  limited,  and 
it  is  enabled  to  act  as  a  ligament  to  support  the  weight  of  the  body 
without  fatigue.*  It  is  inserted  into  the  capsular  ligament  of  the 
elbow  joint,  and  the  rough  tuberosity  at  the  head  of  the  radius.  It 
raises  the  forearm,  and  is  one  of  the  muscles  on  which,  in  part,  the  high 

•  See  description  of  serratus  muscle,  page  62. 


74 


THE    HORSE   IN    MOTION. 


action  of  the  knee  depends.  The  other  is  the  humeralis  externus  of 
Percivall.  It  originates  behind  and  below  the  head  of  the  humerus, 
and,  winding  around  that  bone,  fills  the  furrow  of  torsion  (Plate  II.,  34). 
It  is  inserted  into  the  anterior  heads  of  the  radius  and  ulna,  and  acts 
as  an  assistant  to  the  flexor  brachii :  the  two  muscles  originate  from 
opposite  sides,  but  act  as  a  unit  lifting  the  forearm.  It  has  greater 
power  than  its  associate,  being  larger  and  more  muscular,  and  from 
its  spiral  course  its  fibres  are  longer ;  it  is  capable,  therefore,  of  giving 
higher  action  than  its'  associate. 

The  triceps  of  the  arm  is  a  powerful  muscle  which  plays  a  very 
important  part  in  the  mechanism  of  the  anterior  extremity.  As  its 
name  implies,  it  is  a  three-headed  muscle,  if  we  choose  to  consider  it 
one  muscle,  and  it  is  an  extensor;  but  the  correspondence  in  name 
with  the  triceps  extensor  of  the  thigh  should  not  lead  us  to  confound 
its  mechanism  with  that  of  the  latter.  The  triceps  of  the  arm 
(Plate  IV.,  K)  fills  the  angular  space  between  the  point  of  the  elbow 
(olecranon  process)  and  the  lower  border  of  the  scapula.  The  infra- 
spinatus,  i  s,  covers  the  origins  of  the  three  heads,  but  their  com- 
mon insertion  at  the  short  end  of  the  ulna,  as  their  lever,  is  clearly 
shown  in  a  strong  tendon.  The  two  upper  heads  are  attached  to  the 
lower  border  of  the  scapula,  and  when  these  divisions  contract  they 
tend  to  close  the  angle  between  these  bones ;  but  the  third,  or  lower 
head,  is  not  attached  to  the  scapula,  but  to  the  posterior  face  of  the 
humerus.  This  branch,  sometimes  called  the  short  extensor,  being 
independent  of  the  scapula,  may  act  in  extending  the  arm  when  the 
angle  formed  by  the  latter  bone  and  the  humerus  is  so  small  that 
the  limit  of  contraction  of  the  other  two  branches  is  reached,  as  is  the 
case  in  every  instance  before  the  fore  foot  leaves  the  ground  in  run- 
ning. The  triceps  is  a  powerful  combination  of  muscles.  Its  length, 
varies  with  the  distance  from  the  joint  at  the  shoulder,  being  seven- 
teen inches  at  its  greatest  and  eight  at  the  least  distance.  Its  weight 
which  is  eight  pounds,  does  not  give  a  full  conception  of  its  power, 
for  its  action  is  nearly  direct. 

The  anconeus  is  a  small  muscle  attached  to  the  capsular  ligament 
of  the  elbow  joint,  and  is  inserted  into  the  olecranon  process  of  the 


THE    HORSE    IN    MOTION.  75 

ulna,  or  point  of  the  elbow.  It  contracts  synchronously  with  the 
triceps,  and  its  action  is  upon  the  capsular  ligament  to  pull  it  out 
of  the  way  and  prevent  its  being  pinched  in  the  elbow  joint  as  it 
becomes  relaxed  in  the  extension  of  the  forearm. 

The  muscles  of  the  forearm  are,  like  those  of  the  posterior  ex- 
tremity, simple  and  direct  in  their  action  in  extending  and  flexing 
their  levers,  and,  like  those  of  the  foot,  their  functions  have  been 
well  studied  and  are  well  known.  But  the  complex  forces  are  the 
more  difficult  to  understand  the  nearer  we  approach  their  sources, 
and  have  led  to  great  diversity  of  opinion ;  the  manner  in  which  a 
movement  was  produced  could  not  be  explained  for  the  reason  that 
the  motion  itself  was  not  understood.  Now  that  the  camera  has  ren- 
dered those  motions  easy  of  analysis,  it  is  not  difficult  to  show  how 
they  are  produced. 

The  corresponding  angles  being  reversed,  the  anatomical  relations 
of  the  great  flexors  of  the  feet  are  changed.  In  the  posterior  limbs 
their  tendons  passed  over  the  angles  of  the  hock  to  be  inserted  into 
the  bones  of  the  feet.  In  the  anterior  extremities  the  corresponding 
tendons  are  enclosed  in  a  sheath  of  the  strongest  possible  construc- 
tion, into  the  outer  wall  of  which  the  pisiform  bone  is  placed,  to  afford 
better  protection  to  the  tendons  in  the  flexions  of  the  knee  joint,  which 
is  double,  so  that  when  the  flexion  of  one  is  completed  it  is  continued 
in  the  other,  and  greater  flexion  of  the  metacarpus  upon  the  radius 
is  effected  than  would  be  possible  were  the  joint  single.  It  will  be 
noticed,  on  reference  to  the  silhouettes,  that  the  knee  is  never  bent 
when  the  corresponding  foot  is  on  the  ground.  It  plays  its  part  in  the 
role  of  a  crutch  consistently,  but  it  performs  a  lively  part  in  another 
character  when  relieved  from  the  weight  of  that  responsibility. 

The  tendons  of  the  perforatus  and  perforans  are  utilized  as  liga- 
ments as  in  the  posterior  extremities,  but  with  some  variations  rendered 
necessary  by  the  different  conditions.  From  the  posterior  surface  of  the 
metacarpus,  or  cannon  bone,  below  the  knee,  a  ligament  is  thrown  out 
to  the  perforans  tendon  to  reinforce  it,  and  other  ligaments  or  tendinous 
connections  are  made  to  prevent  extension  of  the  joints  beyond  that 
of  the  standing  position,  by  which  the  tension  is  taken  from  the  flexor 


76 


THE   HORSE    IN    MOTION. 


muscles,  and  their  tendons  act  as  ligaments,  their  size  being  out  of 
all  proportion  to  their  use  as  tendons ;  and  in  the  extreme  extension 
of  the  pastern  the  strain  comes  upon  both  tendons  and  the  suspensory 
ligament,  and  extension  beyond  that  in  the  standing  position  is  effected 
only  by  the  weight  of  the  body,  and  at  the  expense  of  the  elasticity  of 
all  combined.  While  rupture  of  these  tendons  is  of  rare  occurrence 
under  the  strain  thus  put  upon  them,  the  sheaths  through  which  they 
glide  above  the  pastern  are  not  unfrequently  torn  transversely,  giving 
rise  to  inflammation  and  adhesions. 

It  is  stated  as  a  general  proposition  that  the  tendons  are  inexten- 
sible.  This  statement  requires  qualification.  That  they  are  so  under 
all  ordinary  uses  as  tendons  must  be  admitted,  but  when  they  are  serv- 
ing as  ligaments,  in  concert  with  the  suspensory  ligaments,  they  are 
put  upon  a  strain  that  muscle  is  incapable  of  applying  or  resisting.  It 
is  therefore,  as  we  have  elsewhere  shown,  that  powerful  branches  are 
attached  to  the  cannon  bone  to  relieve  the  muscle  of  a  strain  it  is  not 
capable  of  resisting.  The  organic  tissue  is  tendon,  but  its  use  in  exten- 
sion of  the  foot  beyond  a  certain  point  is  that  of  a  ligament  to  limit 
extension ;  but  as  a  ligament  it  does  not  absolutely  arrest  extension, 
for  it  is  elastic  and  allows  of  further  extension  after  it  is  put  upon  the 
stretch ;  or  the  extreme  extension  that  takes  place  in  the  fetlock,  to 
allow  the  pastern  to  take  a  horizontal  position,  would  not  be  pos- 
sible. Further  proof  of  this  will  be  given  after  a  quotation  from  Mr. 
Percivall,  which  I  shall  give  in  extcnso,  for  the  reason  that  the  informa- 
tion conveyed  by  it  is  very  important,  and  few  in  America  will  have  an 
opportunity  to  consult  his  works,  from  their  extreme  rarity. 

"  The  parts  sprained  are  naturally  supposed  to  be  '  the  sinews.'  But 
sinews  or  tendons,  being  both  inelastic  and  (per  physical  force)  inexten- 
sible,  they  themselves  can  neither  be  stretched  nor  strained  so  long  as 
they  maintain  their  cohesion  of  substance.  To  discover,  therefore,  in 
what  part  the  sprain  or  lesion  is  likely  to  be  situate,  it  will  be  advisable 
to  submit  the  leg  in  its  normal  state  to  anatomical  examination. 

"  If  we  strip  or  dissect  off  the  skin  from  the  flexor  tendons,  \ve  find 
underneath,  between  them  and  the  skin,  a  quantity  of  loose  cellular 
tissue,  cutting  away  which  we  come  to  a  close,  or  proper,  tunic  of  the 


THE   HORSE    IN    MOTION.  77 

same  substance  immediately  enveloping  the  tendons.  This  under,  or 
proper,  covering,  however,  is  fibrous  as  well  as  cellular  in  composi- 
tion. For  the  space  of  a  hand's  breadth  below  the  knee  the  glistening 
(tendinous)  fibres  may  be  seen  crossing  obliquely  over  the  tendons,  as 
they  run  from  the  annular  ligament  of  the  knee  to  be  implanted 
into  the  external  border  of  the  cannon  bone  behind  the  external 
splint  bone.  This  forms  the  sheath  of  the  tendons.  And  when  we 
slit  it  open  we  discover  a  cavity  possessing  a  surface  of  a  synovial 
nature  ;  and  a  sac,  or  dursa,  thereby  formed,  which  extends  half-way 
down  the  leg,  and  is  then  closed.  Through  the  bursa  runs  the  per- 
forans  tendon,  which  may  indeed  be  said  to  form  a  posterior  boundary 
to  it.  The  interval  between  the  flexor  tendons  and  the  suspensory 
ligament,  in  their  front,  is  likewise  filled  with  interuniting  cellular  sub- 
stance. This  brief  and  imperfect  anatomical  sketch  may  serve  to  illus- 
trate the  nature  of  sprain.  It  will  at  once  strike  us  that,  although 
the  tendons  themselves  are  incapable  of  extension,  and  are  too  firm 
ind  strong  in  their  texture  to  sustain  hurt  from  any  common  accident, 

that  they  are  surrounded  and  connected  together,  as  well  as  to  the 
aarts  contiguous  to  them,  by  a  soft,  delicate  tissue  which  must,  every 
ime  they  are  forcibly  pulled  or  stretched,  be  extremely  liable  to  stretch 
and  lacerate  ;  and  this,  in  fact,  it  is  which  in  all  ordinary  cases  consti- 
tutes the  true  and  sole  nature  of  '  sprain  of  the  back  sinews.'  " 

What  is  proved  from  the  facts  presented  in  the  above  quotation 
is  that  laceration  of  the  sheath  of  the  tendons  could  not  take  place  ex- 
cept by  the  elongation  of  the  tendon  itself,  and  on  that  elasticity,  or 
spring,  of  these  tendons,  in  conjunction  with  that  of  the  suspensory 
ligament  proper,  the  mechanical  action  depends  and  in  it  their  chief 
value  consists. 

The  action  of  the  anterior  extremity  as  a  unit  in  locomotion  may 
now  be  studied.  As  the  limb  is  thrown  forward  and  in  the  act  of 
taking  the  ground,  it  forms  a  straight  line  from  the  elbow  to  the  heel ; 
the  toe  is  raised,  as  in  the  posterior  extremity,  and  contact  is  made 
with  the  heel.  When  the  weight  comes  upon  the  foot  the  suspensory 
ligament  is  put  upon  the  stretch  by  the  reflexion  of  the  pastern.  The 
knee  is  kept  in  a  straight  position  by  the  tension  of  the  extensors, 


78 


THE   HORSE  IN    MOTION. 


while  the  impulse  is  transmitted  to  the  humerus  at  the  angle  of  the 
elbow,  too  rapid  flexion  at  that  joint  being  prevented  by  the  force  of 
the  triceps  at  the  point  of  the  elbow  and  the  contraction  of  the  great 
pectoral,  which,  acting  on  the  shoulder,  prevents  the  sudden  flexion  of 
that  joint,  at  the  same  time  that  it  forces  the  body  over  the  limb  ;  in 
which  action  it  holds  an  analogous  relation  to  the  vastus  of  the  pos- 
terior extremity,  the  application  of  mechanical  power  being  utterly  dis- 
similar, but  the  result  in  locomotion  the  same.  The  great  dorsal  aids  in 
this  office,  though  less  efficiently.  The  superspinatus,  acting  from  the 
scapula  upon  the  upper  end  of  the  humerus  over  the  shoulder  joint,  per- 
forms the  same  function  for  that  joint,  preventing  its  flexion  too  rapidly. 
The  traction  of  the  triceps  upon  the  scapula  is  so  great  that  it  would 
be  torn  away  from  its  position  but  for  the  counter  action  of  the  trachelo 
subscapularis,  which  transmits  it  to  the  cervical  vertebra,  as  already  ex- 
plained. In  this  order  the  angles  at  the  shoulder  and  elbow  close  while 
the  fetlock  joint  is  bent  until  the  pastern  is  horizontal  with  the  ground. 
In  this  action  the  limb  is  practically  shortened,  until  from  the  position 
of  the  hypothenuse  it  becomes  the  perpendicular  of  a  right-angled 
triangle,  and  during  this  change  of  position  it  has  given  uniform 
support  to  the  centre  of  gravity  without  deviation  of  the  direct  line  of 
its  motion.  During  this  time  the  levator  anguli  scapulas  has  been 
contributing  its  force  by  acting  on  the  short  end  of  the  lever,  drawing 
it  forward  and  adjusting  the  axis  of  the  limb  to  its  changing  require- 
ments. The  passing  of  the  body  over  the  limb  in  a  position  perpen- 
dicular to  the  ground  enables  the  limb  in  its  character  as  an  automaton 
to  exert  a  propelling  force  as  well  as  a  sustaining  one.  It  is  necessary, 
however,  that  the  support  should  be  constant,  as  before;  the  angles  must 
open  as  gradually  as  they  had  closed,  and  the  fetlock  joint  must  be  as 
gradually  straightened.  Some  changes  take  place  in  the  action  of  the 
forces.  The  superspinatus,  that  had  been  yielding  to  allow  of  flexion, 
now  contracts  with  greater  force,  and  its  labor  is  rendered  easy  by  the 
continued  traction  of  the  two  great  propellers  acting  from  the  thorax. 
The  branches  of  the  triceps  acting  from  the  scapula  relax  altogether ; 
that  from  the  humerus  by  its  continued  contraction  extends  the  fore- 
arm upon  the  humerus.  This  order  continues  to  the  close  of  the  first 


THE   HORSE    IN    MOTION.  79 

half  of  the  stride,  when  it  is  in  the  power  of  the  animal  to  give  an 
impulse  to  the  movement,  that  settles  effectually  the  question  of  the 
power  of  the  anterior  extremity  as  a  propeller.  The  proof  will  be 
given  hereafter,  but  the  modus  operand!  is  as  follows:  As  the  foot 
is  about  to  leave  the  ground,  the  angles  of  the  limb  being  extended  to 
their  utmost,  the  great  pectoral,  the  great  dorsal,  and  the  great  serratus, 
by  a  vigorous  and  simultaneous  effort,  in  conjunction  with  the  spring 
of  the  suspensory  ligament  and  its  reinforcing  tendons,  are  capable  of 
deflecting  the  centre  of  gravity  of  the  whole  body  of  the  horse,  going 
with  a  velocity  of  twenty  miles  an  hour,  four  inches  in  a  distance 
of  ten  feet ! 

At  the  completion  of  the  stride,  the  last  impulse  given  by  the 
reaction  of  the  suspensory  ligament  is  like  the  spring  of  a  bow,  and 
the  flexor  muscles  regain  control  of  their  tendons,  which  had  just  been 
serving  as  reinforcements  to  the  suspensory  ligament. 

At  this  moment,  the  foot  being  off  the  ground,  the  knee  bends 
under  the  contraction  of  the  perforatus  and  perforans  muscles.  The 
niperspinatus  and  all  the  muscles  of  the  triceps  are  relaxed  ;  the 
flexors  of  the  shoulder  and  of  the  arm  contract ;  at  the  same  time  the 
mastoido  humeralis  and  superficial  pectoral,  acting  on  the  shoulder, 
carry  the  whole  limb  forward  on  its  centre,  the  great  pectoral  and 
great  dorsal  consenting.  In  this  order  they  pass  the  perpendicular, 
when  the  order  is  quickly  reversed ;  in  twice  the  speed  used  in  the 
retrograde  movement,  the  foot  is  again  in  position  to  take  the  ground. 
The  extensors  of  the  feet,  after  a  rest  of  three  fourths  of  a  stride,  again 
straighten  the  knee,  raise  the  toe,  and  the  triceps  is  ready  with  all  its 
heads  to  take  the  shock.  The  sterno  prescapularis  pulls  the  slack  out 
of  all  the  tissues  connecting  the  shoulder  with  the  trunk,  that  nothing 
may  be  lost  to  effect  the  last  line  in  extension. 

The  action  of  the  anterior  extremity  in  the  three  characters  whose 
parts  it  performs  at  the  same  time,  we  have  endeavored  to  represent.  In 
these  three  characters  it  is  a  complicated  machine.  The  object  in  its 
construction  was  to  enable  the  limb  to  support  the  body  for  the 
greatest  length  of  time,  and  to  graduate  that  support  so  that  it  should 
be  uniform  and  constant,  and  that  there  should  be  no  loss  of  momen- 


8o 


THE    HORSE    IN    MOTION. 


turn  or  waste  of  power  by  correcting  deflection  of  the  line  in  which  it 
is  intended  the  body  shall  move.  This  rendered  necessary  the  use  of 
the  legs  alternately,  so  that  while  one  should  be  performing  these 
functions  the  other  should  be  moving  in  the  reverse  direction,  to  take 
its  place  and  permit  as  little  loss  of  time  as  possible  between  the  end 
of  the  performance  of  one  limb  and  the  beginning  of  that  of  the  next. 

If  we  have  comprehended  the  movements  of  a  limb  and  the  relative 
value  of  the  forces  that  produce  them,  the  levers  on  which  they  act 
and  the  relation  of  the  limbs  to  each  other,  we  ought  to  be  able  to 
determine  the  mechanical  elements  of  the  qualities  desired  in  a  horse. 
If  speed  is  desired  we  must  look  for  those  mechanical  conformations 
of  parts  that  determine  speed,  but  this  speed  must  be  attained  at  the 
expense  of  power.  The  anterior  limbs  must  conform  in  their  mechan- 
ical force  to  the  posterior,  and  vice  versa.  It  was  observed  of  the  pos- 
terior limbs  that  long  full  propellers  (the  vasti  and  glutei),  low  hip  joint 
set  well  back,  so  as  to  afford  room  for  long  femur  and  tibia,  gave  great 
length  of  limb  when  extended,  enabling  it  to  support  the  weight  of  the 
body  and  exert  its  propulsion  for  a  longer  time,  at  the  same  time  the 
power  was  more  directly  applied  when  the  head  of  the  bone  was  lower 
down.  So  far  as  these  principles  can  be  applied  to  the  anterior  limbs 
they  hold  true  of  them  as  of  the  posterior  extremities. 

It  was  observed  by  Bishop  that  all  animals  distinguished  for  great 
speed  have  the  angles  of  the  bones  most  inclined  to  one  another.  But 
while  this  mechanical  arrangement  gives  great  advantage  for  speed  it 
is  a  source  of  weakness  in  bearing  burdens  and  hauling. 

The  requirements  for  the  anterior  extremities,  to  be  in  harmony 
with  the  posterior  ones,  would  be  a  long  oblique  scapula  and  long 
humerus :  these  bones  long,  the  angle  formed  by  them  would  neces- 
sarily be  less  obtuse.  The  great  pectoral  and  great  dorsal  are  the 
muscles  that  hold  the  mechanical  relation  to  the  anterior  extremity 
that  the  great  gluteus  and  vastus  do  to  the  posterior;  and  to  give  equal 
advantage  to  them  the  thorax  should  be  long  to  give  sufficient  distance 
between  the  ribs  of  origin  and  the  insertion  at  the  shoulder. 

The  application  of  propulsion  to  the  anterior  limb  is  unlike  that  to 
the  posterior,  and  as  it  is  an  advantage  in  the  latter  to  have  the  heads 


THE    HORSE    IN    MOTION.  8 1 

of  the  femurs  low  down  to  push  more  directly,  in  the  former,  on  the 
contrary,  the  centre  of  motion  corresponding  to  the  head  of  the 
femur  is  not  at  the  shoulder,  but  as  high  under  the  withers  as  pos- 
sible, and  the  application  of  the  propulsion  as  low  as  possible,  as 
was  shown  when  describing  the  action  of  the  great  pectoral ;  for, 
the  foot  being  the  fixed  point,  the  nearer  the  power  is  applied  to  it 
the  greater  will  be  the  velocity  of  the  upper  end  of  the  extremity 
acting  as  a  crutch. 

In  the  extreme  of  flexion  and  extension,  as  represented  in  leaping, 
the  muscles  act  at  great  disadvantage,  as  is  illustrated  by  the  difficulty 
and  slowness  with  which  an  animal  rises  from  a  recumbent  posture. 
They  are  positions  incompatible  with  speed. 

Whether  the  muscles  act  with  the  greatest  energy  at  the  earlier  or 
later  stage"  of  contraction  has  not  been  determined  with  certainty  as 
far  as  I  know.  There  is  no  doubt,  however,  that  they  act  with  the 
greatest  promptitude  in  response  to  the  will  when  the  limbs  are 
.-lightly  flexed.  Boxers  will  instinctively  put  themselves  in  that  po- 
sition when  in  attitude  for  offence  or  defence.  Boys  when  about 
to  start  for  a  race  will  relax  their  extensors  to  get  a  good  send-off,  and 
they  do  not  fully  extend  them  again  until  the  trial  of  speed  is  over. 
So  the  horse  in  fast  trotting  "settles  to  his  work,"  as  it  is  technically 
called.  In  this  expression  it  is  intended  to  represent  the  idea  that 
the  centres  of  motion  are  nearer  the  ground  in  order  that  the  muscles 
shall  act  to  the  best  advantage,  and  that  in  propulsion  the  act  shall  be 
most  direct  and  longer  sustained ;  or,  in  other  words,  the  points  of 
action  and  reaction  are  in  a  line  forming  a  more  acute  angle  with 
the  ground. 

M.  Weber  asserted  that  the  velocity  in  walking  will  be  greater  the 
nearer  the  head  of  the  femur  is  to  the  ground ;  as  this  height  in- 
creases the  velocity  decreases.  One  sometimes  arrives  at  a  truth  by 
a  very  devious  route,  though  he  may  have  lost  himself  on  the  way. 
He  proved  his  position  by  the  pendulum,  which  has  been  made  to 
demonstrate  many  a  knotty  proposition  ;  but  while  the  leg  of  his 
physical  horse  has  swung  three  feet,  our  living  horse  has  gone  forty, 
and  his  extremities  have  performed  two  complete  revolutions.  The 


82 


THE    HORSE    IN    MOTION. 


speed  of  the  horse  does  not  depend  upon  the  length  of  the  limbs 
acting  as  pendulums,  but  upon  the  length  and  thickness  of  the 
locomotor  muscles,  the  angles  and  lengths  of  the  bony  levers  on 
which  they  act,  the  freedom  of  their  articular  ligaments,  the  corre- 
lation of  all  the  mechanical  parts,  and  much  also  on  the  nervous 
energy  or  will  transmitted  to  the  muscles,  technically  known  as 
courage. 


CHAPTER    V. 

IXFLUFXCF.  OF  CKAVITY  CONSTANT. —  MOMENTUM  ACCELERATED.  —  THE  LAW  OF  FALL- 
IXC,  BODIES  AND  ITS  APPLICATION  TO  LOCOMOTION.  —  THE  NEARER  THE  TRAJF.C- 
TORY  OF  THE  CENTRE  OF  GRAVITY  IS  TO  A  STRAIGHT  LINE  THE  MORE  PERFECT 
THE  LOCOMOTION.  —  THE  THEORY  OF  QUADRUPEDAL  LOCOMOTION  STATED.  —  ANAL- 
YSIS OF  THE  RUN.  —  THE  SAME  IN  ALL  THE  DOMESTIC  ANIMALS. — THE  BOUND  OF 
THE  DEER.  —  WHY  THE  FLEXOR  TENDONS  OF  THE  FORE  LEGS  ARE  MORE  LIABLE 
TO  HE  INJURED  IN  THE  RUN. — WHAT  IS  THE  GALLOP  ?  — OBJECTIONS  OF  ARTISTS 
ANSWKKED. — TRUTH  MUST  PREVAIL  OVER  CONVENTIONALISM.  —  THE  CANTER. 

THE  attraction  of  gravity,  or  that  force  which  is  constantly  drawing 
all  bodies  toward  the  centre  of  the  earth,  is  a  phenomenon  so  familiar 
to  us  that  we  fail  to  realize  it  at  all  times,  and  the  consequences  that 
would  ensue  were  it  to  be  for  one  moment  suspended.  Like  the  air 
we  breathe,  it  is  one  of  the  necessary  conditions  of  our  existence,  and 
the  force  with  which  it  acts  on  all  bodies  is  exactly  measured  by  their 
weight;  but  this  is  the  measure  of  that  force  in  bodies  in  a  state  of 
rest  or  inertia.  The  instant  that  support  is  removed  and  the  body 
yields  to  that  force,  there  enters  another  element  that  must  be  taken 
into  account,  and  that  is  momentum.  While  gravity  is  a  constant 
quantity  under  similar  conditions,  momentum  is  a  constantly  varying 
one. 

By  yielding  to  the  force  of  gravity  an  object  does  not  escape  from 
its  power,  neither  is  it  reduced  one  grain  in  its  influence  at  whatever 
rate  the  body  falls.  It  is  therefore  an  increasing  quantity  in  a  rapid 
ratio.*  It  is  this  force,  which  is  constant  and  measured  by  the  weight 

*  The  formula  for  the  determination  of  the  distance  which  a  body  will  fall  in  any  given 
time  is,  D  =  J  g  f  •  in  which  D  =  distance  ;  g,  acceleration  of  gravity,  or  32  feet ;  /,  time 
in  seconds.  From  this  we  learn  that  the  distance  which  a  body  unsupported  would  fall  in  the 
first  \  second  would  be  4  feet ;  in  the  first  \  second,  7.68  inches  ;  in  the  first  J  second,  3  inches. 


84  THE   HORSE    IN    MOTION. 

of  the  horse,  that  renders  necessary  the  great  development  of  the  loco- 
motive organs  and  columns  of  support.  The  power  of  resistance  of 
these  organs  must  be  equal  to  the  attraction  of  gravity  and  counteract 
it,  and  at  the  same  time  be  in  such  excess  as  will  afford  .the  means  of 
propulsion  in  a  horizontal  direction.  The  influence  of  gravity  is  not 
affected  by  motion  in  the  body  subject  to  it,  at  whatever  rate  it  may 
be  moving.  It  may  be  projected  into  the  air  by  a  force  greater  than 
that  of  gravity,  but  it  does  not  escape  from  it  in  any  degree.  The 
force  that  projected  it  was  stronger  than  that  of  gravity  at  the  time  of 
the  impulse  ;  but  the  resistance  of  the  air  and  the  constant  force  of  grav- 
ity would  soon  bring  the  motion  to  an  end  without  the  continuation 
of  that  projectile  force. 

It  is  the  result  of  this  continuation  of  force  in  such  directions  as  will 
resist  the  attraction  of  gravity,  and  overcome  resistance  to  a  movement 
in  a  horizontal  direction,  that  we  call  locomotion. 

There  is  another  physical  law  to  the  effect  that  a  body  put  in  mo- 
tion will  continue  in  motion  in  the  given  direction  until  diverted  by 
another  force  from  another  direction.  The  force  with  which  a  body 
moves  above  the  surface  of  the  ground  is  determined  by  multiplying 
its  weight  by  its  velocity,  and  is  called  its  momentum ;  therefore  the 
force  of  gravity,  represented  by  the  weight,  being  constant  in  the  same 
body,  the  momentum  will  be  as  the  velocity.  If  the  body  be  repre- 
sented by  an  iron  ball  weighing  one  thousand  pounds,  moving  at  the 
rate  of  twenty-five  miles  an  hour  in  a  horizontal  direction,  it  will 
represent  the  momentum  of  a  horse  of  equal  weight  at  full  speed. 
To  arrest  it  suddenly  would  be  its  destruction. 

To  continue  its  motion  without  diminution  of  velocity  requires  a 
continuous  application  of  force,  and  the  greater  the  velocity  the  greater 
is  the  necessity  that  the  trajectory  or  line  of  motion  should  suffer  no 
deflection,  for  the  force  necessary  to  correct  it  increases  with  the 
momentum. 

From  what  has  been  said  it  follows  that  the  only  muscular  power 
required  to  keep  a  body  in  motion,  at  whatever  speed,  is  that  which  is 
necessary  to  resist  the  attraction  of  gravity  and  overcome  resistance. 
It  is  plain  that,  in  order  to  maintain  a  uniform  support  of  gravity,  and 


THE   HORSE    IN    MOTION  85 

a  continuous  impulse  in  the  direction  of  motion,  the  limbs  must  move, 
at  whatever  pace,  in  such  manner  as  best  to  attain  that  end;  that  the 
more  rapid  the  motion,  the  more  uniform  must  be  the  support. 

If  the  time  occupied  by  a  racing  horse  in  going  a  mile  be  one 
minute  and  forty  seconds,  and  the  length  of  stride  twenty-five  feet, 
as  represented  of  some  horses,  it  would  follow  that  he  must  be  off  the 
ground  a  full  half-second  at  each  bound,  and  according  to  the  law  of 
falling  bodies  he  would,  if  he  moved  horizontally,  during  that  time  fall 
a  distance  of  four  feet.  But  in  the  gallop  he  is  supposed  to  be  moving 
by  a  succession  of  bounds  in  which  he  rises  as  far  as  he  falls.  This 
would  give  one  fourth  of  a  second  as  the  time  of  descent  equal  to  one 
foot  of  vertical  fall  to  twelve  and  a  half  feet  movement  in  a  horizon- 
tal direction,  and  a  consequent  deflection  of  the  centre  of  gravity  to 
that  extent. 

We  can  imagine  the  effect  that  would  be  produced  upon  a  railway 
car  of  any  description  if,  when  going  at  the  same  rate,  it  should  pass 
over  an  obstruction  that  would  produce  such  a  deflection  of  the  line  of 
motion ;  and  if  instead  of  the  railway  car  we  substitute  the  horse,  what 
but  a  broken  neck  could  be  expected  ?  There  is  no  suspensory  lig- 
ament, or  back  tendon,  or  joint  of  the  body  that  could  be  submitted  to 
such  a  shock  in  a  state  of  tension,  and  not  go  through  bankruptcy 

It  is  this  deflection  in  the  line  of  motion  that  constitutes  the  great 
obstacle  to  be  overcome  in  all  methods  of  locomotion.  It  is  that 
which  retards  the  progress  of  a  ship  in  a  rough  sea;  a  certain  amount 
of  momentum  is  lost  in  every  undulation,  and  power  is  spent  in  lifting 
the  ship  against  the  force  of  gravity  that  might  in  a  smooth  sea  be 
spent  in  accelerating  velocity.  But  a  ship  is  an  inanimate  object 
acted  upon  by  inanimate  forces,  and  though  speed  is  sacrificed,  there 
is  no  exhaustion  from  waste  of  strength,  as  is  sustained  by  all  living 
beings  in  contending  against  the  law  of  gravity,  which  requires  a 
greater  expenditure  of  force  to  arrest  a  body  in  its  fall  than  is  required 
to  sustain  it  in  a  state  of  rest. 

The  most  perfect  method  of  quadrupedal  locomotion,  therefore,  is 
that  in  which  the  greatest  speed  is  attained  with  the  least  expenditure 
of  vital  force.  This  is  found  in  those  quadrupeds  in  which  the  devia- 


86 


THE    HORSE    IN    MOTION. 


tion  of  the  line  of  motion  from  the  horizontal  is  least.  Pre-eminent 
among  these  are  the  horse  and  hound,  whose  mode  of  progression  is 
the  same.  Though  the  deer  and  hare  may  have  the  advantage  for 
a  short  run,  yet  the  method  of  progression  by  bounds,  used  by  these 
animals,  sooner  fatigues  them,  and  in  a  fair  field  they  will  be  run  down 
by  the  former  from  sheer  exhaustion.  To  this  subject  we  shall  refer 
again  when  we  analyze  the  paces  of  the  deer  and  dog. 

In  the  two  preceding  chapters  we  have  condensed  the  anatomy  of 
the  locomotive  organs  into  as  small  a  space  as  possible,  and  at  the 
same  time  have,  with  the  aid  of  accurate  drawings,  endeavored  to 
make  the  mechanical  action  of  all  the  limbs  individually  so  intelligible 
that  any  one  of  ordinary  information  may  comprehend  them.  We  will 
now  proceed  to  show  how  these  forces  are  co-ordinated  in  the  produc- 
tion of  the  different  paces  when  all  the  limbs  are  in  action.  Instead 
of  the  mingled  confusion  of  limbs  and  display  of  brute  force,  one  may 
see  the  most  perfect  order  and  regularity.  In  the  slow  movements 
the  limbs  of  the  horse  are  without  doubt  much  under  the  control  of 
the  will ;  he  may  use  his  anterior  ones  to  strike,  paw  the  ground,  and 
in  various  ways  show  the  control  he  has  of  different  muscles  in  the 
performance  of  their  various  functions ;  he  may  rear  and  kick,  toss  his 
head  and  lower  it  to  the  ground,  as  in  drinking,  grazing,  or  sauntering; 
but  when  speeding,  whether  from  ambition  or  terror,  all  this  trifling  is 
laid  aside,  the  position  of  the  head  becomes  fixed  as  a  base  of  action 
for  the  muscles  of  the  neck  and  head,  the  detailed  action  of  the  va- 
rious parts  of  the  animal  are  lost  in  the  complicated  machine,  and 
the  whole  acts  automatically,  as  the  movements  of  the  various  parts 
of  a  locomotive  are  lost  in  the  combined  action  of  the  engine  to 
which  they  are  subordinate. 

The  run  is  the  perfect  gait  of  the  horse,  for  it  is  that  which  displays 
most  perfectly  the  play  of  all  his  locomotive  organs,  by  which  he  at- 
tains his  greatest  speed,  and  to  which  he  owes  his  preservation  in  the 
long  struggle  for  existence  through  which  he  must  have  passed  before 
he  came  under  the  protecting  care  of  man.  It  is  the  gait,  therefore, 
which  best  serves  as  a  subject  to  study  the  law,  or  the  theory  of  his 
locomotion.  To  any  one  who  has  followed  the  anatomical  analysis 


THE    HORSE    IN    MOTION.  87 

of  the  last  t\vo  chapters,  the  theory  may  have  already  outlined  itself; 
but  it  is  desirable  that  it  should  be  made  clear  to  all,  and  many  of  the 
anatomical  facts  demonstrated  in  the  last  chapters  must  be  taken  for 
granted  in  this  by  those  who  have  not  given  the  necessary  attention 
to  the  anatomical  descriptions.  Perfect  quadrupedal  locomotion  re- 
quires uniform  support  to  the  centre  of  gravity  and  continuous  pro- 
pulsion by  each  extremity  in  turn. 

In  order  to  avoid  the  abstract  study  of  the  co-ordination  of  the 
limbs  in  locomotion,  figures  are  given  to  aid  the  mind  in  following  the 
movements.  They  were  executed  by  a  process  called  photo-engraving, 
after  drawings  made  with  great  care  from  a  series  of  photographs,  and 
represent  twelve  views  of  as  many  positions  of  a  running  horse.  Three 
horizontal  lines  are  drawn  above  the  base  at  intervals  of  one  hand,  or 
four  inches,  as  a  guide  to  the  eye  in  determining  the  elevation  of  the 
feet,  and  a  fourth  near  tlvj  back  to  show  the  deviation  from  a  horizontal 
line  of  the  centre  of  gravity,  which  we  will  suppose  to  be  under  the 
saddle.  These  cuts  are  not  introduced  for  their  accuracy ;  they  have 
been  subjected  to  too  much  manipulation  to  lay  claim  to  that  precision 
of  outline  that  will  be  found  in  the  heliotypes  and  silhouettes  in  photo- 
lithography given  in  illustration  of  the  paces. 

FIG.  i. 


Fig.  i.  gives  the  position  of  the  animal  in  readiness  to  start, 
height  is  a  little  in  excess  of  sixteen  hands. 


Its 


88 


THE   HORSE    IN    MOTION. 


We  have  inserted  two  plates  of  the  skeleton  in  the  positions  corre- 
sponding with  Figs.  6  and  1 2  in  order  to  enable  the  reader  to  under- 
stand their  action  in  the  various  movements,  and  by  reference  to  Plate 
II.  he  will  be  enabled  to  follow  the  descriptions  in  this  chapter,  and 
the  action  of  the  various  muscles  that  produce  them,  as  described  in 
the  previous  chapters. 

FIG.  2. 


Fig.  2  represents  the  left  fore  foot  upon  the  ground  nearly  under 
the  centre  of  gravity;  the  centre  of  motion  for  the  corresponding  limb 
has  passed  in  advance  of  the  foot,  and  a  line  drawn  through  these  two 
points  would  not  be  perpendicular  to  the  surface  of  the  ground  ;  or,  for 
brevity  of  expression,  we  will  say  he  has  passed  the  perpendicular. 
The  limb  is  being  elongated  or  extended  by  the  straightening  of  the 
pastern  joint  and  the  joints  at  the  elbow  and  shoulder ;  by  these  means 
the  support  given  by  the  muscles  is  continued.  In  this  position  there 
is  no  muscular  force  exerted  upon  this  limb  below  the  knee.  It  was 
shown  at  page  76  how  the  "  back  tendons,"  while  the  limb  is  in  this 
position,  are  converted  into  ligaments  over  which  their  muscles  have 
for  the  instant  surrendered  control,  and  in  conjunction  with  the  suspen- 
sory ligament  are  supporting  the  weight  of  the  body  by  their  passive 
resistance.  As  the  body  advances  by  its  own  momentum  and  the  con- 
tinual action  of  the  great  pectoral  and  dorsal  muscles,  the  pastern  joint 


THE    HORSF.    IN    MOTION.  89 

becomes  nearly  straight,  and  the  pastern  bone  resumes  its  position 
under  the  metacarpus,  or  cannon  bone,  and  while  that  joint  is  still 
supported  at  its  convex  posterior  surface  by  these  powerful  ligaments ; 
and  as  the  limit  of  extension  is  reached  and  the  limb  is  at  an  angle 
with  the  ground  of  forty-five  degrees,  a  vigorous  concerted  action  of  the 
propellers  sends  it  forward  and  upward  in  the  direction  of  the  axis  of 
the  limb  with  a  force  so  great  as  to  close  the  space  between  the  croup 
and  the  gauge  line  above  it,  and  all  his  feet  are  in  the  air.  If  this  force 
had  been  applied,  as  is  popularly  supposed,  by  the  posterior  extremity 
and  behind  the  centre  of  gravity,  the  result  would  inevitably  have  been 
to  pitch  the  animal  headlong  to  the  ground.  The  position  of  the  fore 
leg  just  before  it  leaves  the  ground  is  best  shown  in  Fig.  12. 

FIG.  3. 


Fig.  3  shows  the  feet  all  in  the  air.  The  foot  which  rested  last 
upon  the  ground  is  now  eleven  inches  above  it  and  moving  rapidly 
to  the  front.  The  interval  of  time  between  the  photograph  of  the 
horse  in  position  No.  2  and  that  of  No.  3  was  greater  than  that  which 
passed  between  No.  3  and  No.  4,  owing  to  want  of  uniformity  in  the 
tension  of  the  threads  making  the  magnetic  circuit.  This  defect  was 
subsequently  remedied  ;  and  in  the  series  of  views  illustrating  the  run, 
in  which  the  gait  was  more  thoroughly  analyzed  by  a  larger  number 
of  cameras,  the  intervals  are  very  regular. 


9o 


THE   HORSE    IN    MOTION. 


FIG.  4. 


In  No.  4  the  upward  impulse  given  by  the  fore  leg  may  be  supposed 
to  have  reached  its  limit,  the  croup  having  passed  above  the  gauge- 
line  marking  the  elevation,  and  the  feet  are  all  gathered  under  the 
trunk  more  than  a  foot  above  the  ground.  There  is  now  an  oppor- 
tunity for  the  animal  to  change  their  order ;  for,  as  has  been  stated, 
he  cannot  change  the  order  of  his  feet  when  one  of  them  is  on  the 
ground,  and  he  is  going  at  a  rapid  rate,  without  subjecting  himself  to 
a  fall.  Although  the  distance  passed  over  from  the  time  the  last  foot 
left  the  ground  until  the  next  one  reaches  it  is  only  equal  to  the 
interval  of  any  of  the  feet,  and  the  time  that  has  elapsed  while  this 
has  been  taking  place  does  not  exceed  perhaps  a  fifth  part  of  a 
second,  still  it  is  sufficient  to  enable  the  animal  to  choose  whether 
he  shall  lead  with  one  foot  or  the  other  in  the  next  stride.  But  the 
time,  short  as  it  is,  is  sufficient  to  cause  a  descent  of  four  inches,  and 
the  momentum  acquired  makes  the  contact  with  the  earth  a  much 
more  serious  matter  than  in  any  other  portion  of  the  stride.  To  make 
it  with  either  of  the  anterior  extremities,  or  both,  as  is  popularly  be- 
lieved to  be  the  case,  would  seriously  check  the  momentum,  if  it  did 
not  result  disastrously  to  the  unlucky  member.  But  this  has  been 
shown  over  and  over,  by  numerous  observations  at  Palo  Alto,  never  to 
take  place  in  running.  The  first  check  to  the  descent  of  the  centre 


THE   HORSE   IN   MOTION.  91 

of  gravity  is  given  by  one  of  the  hind  legs,  and  by  that  one  which 
is  diagonal  to  the  fore  leg  leaving  the  ground 'last;  but,  to  reach 
it  in  such  manner  as  to  prevent  a  catastrophe,  it  must  be  planted 
beneath  the  centre  of  gravity  or  in  advance  of  it,  and  then,  in  order 
to  prevent  the  anterior  part  of  the  body  from  falling  forward,  it  is 
necessary  that  all  the  available  force  should  be  brought  to  bear 
upon  the  right  hind  leg  as  a  lever  with  its  fixed  point  upon  the 
ground.  How  this  is  effected,  and  by  what  muscles,  is  shown  at 
page  58. 


FIG. 


This  situation  is  shown  at  Fig.  5.  The  picture  was  taken  almost  at 
the  instant  of  contact  by  the  right  hind  foot  with  the  ground.  The 
anterior  portion  of  the  body  is  arrested  in  its  downward  course,  not 
by  its  own  limbs,  but  by  the  contraction  of  all  the  muscles  forming 
the  external  periphery  of  his  body,  from  the  neck  to  the  flexors  of  the 
foot ;  by  which  combination  of  forces  the  whole  body  forward  of  the 
head  of  the  femur  is  not  only  arrested  in  its  downward  course,  but 
lifted,  while  the  momentum  in  a  horizontal  direction  is  maintained 
chiefly  by  the  contraction  of  the  vastus  shortening  the  distance  be- 
tween the  lower  extremity  of  the  femur  and  the  spines  of  the  sacrum, 
pushing  the  pelvis  forward  from  its  fossa  behind  the  head  of  the 
femur.  The  body  is  propelled  forward  with  a  part  of  the  same  power 
that  lifts  it.  In  this  manner  it  does  not  check  the  momentum  ac- 


92 


THE   HORSE    IN  MOTION. 


quired,  as  would  have  been  the  case  had  one  of  the  fore  legs  been 
thrust  forward  to  the  ground,  and  the  danger  of  stumbling  is  averted. 


FIG.  6. 


As  progression  continues,  the  limbs  are  all  taking  positions  in  the 
order  they  will  be  required  to  perform  their  functions.  The  right  leg 
in  Fig.  6  is  passing  the  perpendicular;  the  pastern  is  bent  to  the 
ground  to  shorten  the  limb,  and  the  left  hind  foot  is  descending  to 
repeat  the  same  action,  when  the  right,  from  the  advancing  position  of 
the  body,  will  be  unable  to  continue  its  support,  and  the  right  or  diago- 
nal fore  leg  is  straightening  to  take  its  turn  after  the  left  hind  one. 

FIG.  7. 


THE    HORSE    IN    MOTION. 


93 


In  Fig.  7  the  left  hind  foot  is  supporting  the  weight,  and  already  the 
centre  of  gravity  has  passed  over  it,  while  the  right,  relieved  from  that 
duty,  is  exercising  its  function  as  a  propeller,  and  the  right  fore  leg 
is  reaching  forward  to  take  the  ground  as  far  as  possible  in  advance ; 
the  foot  is  extended  to  bring  the  heel,  with  its  elastic  cushion,  first  in 
contact.  The  left  fore  leg  is  straightening  to  take  its  place  in  the 
order  of  succession. 

FIG.  8. 


The  right  hind  leg  has  given  its  final  propulsive  impulse  in  Fig.  8, 
and  the  tensor  vaginas  femoris,  the  iliacus,  sartorius,  and  superficial 
gluteus  are  in  the  act  of  flexing  the  stifle  and  advancing  the  leg  to 
a  new  position.  The  left  hind  leg  has  passed  the  perpendicular,  and  is 
no  longer  in  a  position  to  give  much  aid  as  a  supporter  to  the  centre 
of  gravity ;  but  the  right  fore  foot  has  reached  the  ground,  and  takes 
its  position  as  a  supporter  of  the  weight  of  the  body,  dividing  the 
burden  with  the  left  hind  leg  still  upon  the  ground. 

In  the  last  chapter  it  was  shown  how  the  limb  is  thrown  forward 
into  this  position,  and  how  the  shock  of  contact  is  transmitted,  through 
the  straightened  extremity,  to  the  humerus  and  scapula ;  and  unneces- 
sary flexion  of  the  elbow  and  shoulder  joints  is  prevented  by  the  tri- 
ceps of  the  arm  and  superspinatus  muscles,  while  it  continues  to  give 
uniform  support  to  the  body,  at  the  same  time  that  it  shortens  by  the 


94 


THE   HORSE   IN   MOTION. 


gradual  flexion  of  those  joints  and  the  bending  of  the  fetlock  as  the 
body  passes  over  its  point  of  support. 

The  danger  to  be  apprehended  in  the  use  of  the  fore  leg  to  arrest 
the  downward  movement  when  the  body  was  falling,  as  in  Fig.  5,  does 
not  exist  in  this  position,  as  the  momentum  of  gravity  has  been  ar- 
rested by  the  posterior  extremities,  and  the  centre  of  gravity  has 
reached  its  lowest  point,  while  the  weight  is  divided  with  the  hind  leg. 
Propulsion  is  now  going  on  in  the  fore  leg  through  the  great  pec- 
toral and  dorsal,  and  in  the  hind  leg  through  its  propellers  proper. 

FIG.  9. 


The  right  fore  leg  in  Fig.  9  is  now  taking  the  entire  weight  of  the 
body,  is  nearly  perpendicular,  is  correspondingly  shortened,  and  its 
fellow  is  extended  forward  in  the  position  to  take  its  turn.  The  left 
hind  foot  is  clear  of  the  ground,  and  the  right  has  been  elevated  by  the 
action  of  the  semitendinosus  slightly  flexing  the  stifle.  The  settling  of 
the  body  has  not  varied  much  from  the  position  seen  in  the  last  figure. 
Propulsion  by  the  great  pectoral  and  dorsal  on  the  fore  leg,  which  is 
also  bearing  alone  the  full  weight  of  the  body,  is  most  energetic,  and 
to  the  best  advantage. 

In  the  interval  that  has  passed  between  the  position  of  Figs.  9  anc 
10  the  left  fore  foot  has  descended  twelve  inches,  is  only  four  inches 
from  the  ground,  and  must  be  considered  as  in  the  position  in  whicl 


THE   HORSE    I\   MOTION. 


FIG.  10. 


the  heel  makes  contact  with  it.  The  right  leg  is  elongating,  and 
making  propulsion  by  so  doing,  in  its  function  as  an  automaton  and 
also  as  a  passive  tool,  by  the  great  dorsal  and  pectoral  making  traction 
from  the  flanks  upon  the  shoulder.  The  support  it  is  giving  to  the 
weight  of  the  body  is  shown  by  the  narrowing  of  the  space  between  it 
and  the  gauge  line.  This  action  is  not  yet  complete.  Both  the  hind 
feet  are  nearly  equally  elevated,  but  the  right  leg  is  more  flexed.  The 
increased  flexion  of  the  stifle  renders  necessary  the  flexion  of  the  hock- 


FlG.  II. 


y6 


THE   HORSE    IN   MOTION. 


joint,  for,  as  already  shown,  they  act  together  automatically.  The 
flexors  proper  of  the  thigh  are  now  making  their  force  felt  with  that  of 
the  semitendinosus,  and  the  stifle  is  being  drawn  forward.  The  flexors 
of  the  foot,  being  propelling  muscles,  are  inactive,  and  the  semiflexec 
position  of  the  joints  of  the  feet  is  owing  to  the  reaction  of  the  suspen- 
sory ligaments. 

In  Fig.  1 1  the  right  fore  foot  is  clear  of  the  ground,  and  the  left  is 
in  a  position  corresponding  with  that  of  the  right  in  Fig.  9,  but 
right  is  not  in  a  corresponding  position  with  the  left  in  the  same 
figure.  The  right  hind  foot  is  preparing  to  take  its  place  in  the  order 
of  succession,  to  be  followed  by  the  other  hind  foot  in  its  turn. 


FIG.  12. 


In  Fig.  1 2  the  stride  is  completed.  On  comparison  with  Fig.  2,  it 
will  be  seen  that  the  body  is  advanced  somewhat  beyond  that  in  the 
latter,  and  it  is  again  about  to  leave  the  ground  with  the  left  fore  foot, 
and  the  energy  of  the  propelling  forces  have  already  sent  the  body  up 
nearly  to  the  horizontal  gauge-line.  This  order  in  the  movement  is 
continued  until  the  animal  feels  fatigue  in  the  left  fore  leg  from  the 
continued  use  of  it  in  giving  the  final  impulse  to  clear  the  ground, 
when,  as  before  said,  it  is  in  his  power  to  change  it  and  leave  the 
ground  with  the  other  fore  leg. 


TIIK    IIORSK    IN    MOTION.  97 

It  seems,  at  first  thought,  from  the  manner  in  which  the  labor  is 
thrown  from  the  leading  fore  foot  to  the  diagonal  hind  one,  during 
which  the  body  has  no  support  from  cither,  that  the  theory  of  constant 
support  and  continuous  propulsion  does  not  hold  true,  —  that  a  perfect 
machine  should  require  no  such  hiatus.  If  the  machine  had  been 
constructed  of  inorganic  and  inanimate  material,  incapable  of  fatigue, 
it  could  have  been  so  arranged  that  the  hiatus  would  not  have  been 
necessary;  but  the  Creator  did  not,  if  he  could,  build  an  animate 
machine  that  would  not  tire.  The  animal  is  shown  in  the  above 
figures  as  moving  his  feet  in  the  same  order,  and,  but  for  some  ar- 
rangement that  would  permit  of  a  change,  fatigue  would  be  inevitable; 
but  that  change  would  not  be  possible  until  all  the  feet  are  clear  of 
the  ground.  If  the  attempt  should  be  made  while  one  foot  is  on  the 
ground,  the  result  would  be  called  a  misstep  and  a  fall.  The  opportu- 
nity is  afforded  when  the  extraordinary  propulsive  force,  given  by  the 
fore  leg  that  leaves  the  ground  last,  projects  the  body  upward,  giving 
a  time  equal  to  one  fifth  of  a  stride  for  the  hind  foot  of  the  same  side 
to  take  the  place  of  the  one  that  would  have  followed  had  the  same 
order  continued.  The  coincidence  of  the  act  of  changing  the  order  of 
the  feet  with  the  exposure  of  the  negative  plate  in  the  camera,  which 
is  too  short  a  time  for  computation,  must  be  very  rare,  and  has  not 
been  observed  in  any  of  the  many  pictures  taken  at  Palo  Alto ;  but 
the  change  is  felt  by  the  driver  when  the  feet  again  take  the  ground, 
and  it  is  said  to  have  been  discovered  in  the  changed  order  of  the 
footprints. 

While  the  run  requires  that  each  limb  in  turn  should  act  as 
propeller  and  supporter  in  regular  order,  it  cannot  be  executed  at 
a  low  rate  of  speed,  for  the  base  of  support  is  confined  to  one  foot, 
and  it  must  be  rapidly  adjusted  to  the  changes  of  the  position  of  the 
centre  of  gravity,  for  the  same  reason  that  a  boy  on  stilts  requires 
to  be  continually  in  motion.  If  the  horse's  speed  is  diminished  to 
a  great  degree,  he  will  change  to  a  canter,  which  is  a  pace  modified 
from  the  run,  as  may  be  seen  by  reference  to  Plate  XXVII.,  or, 
what  is  more  usual,  to  a  trot,  in  which  he  uses  two  diagonal  feet  as 
bases  of  support. 

'3 


98  THE    HORSE    IN    MOTION. 

The  order  and  action  of  the  limbs  are  uniform  in  all  the  numerous 
trials  of  running  horses  photographed  at  Palo  Alto ;  so  that  it  may  b 
considered  that  they  are  in  conformity  with  a  law.  Five  series  of  th 
photographs  are  given,  of  horses  representing  different  rates.  Th 
first  is  that  of  "Mohammed,"  whose  stride  is  15  ft.  9  in.;  and  the 
last,  that  of  "  Florence  Anderson,"  with  a  stride  of  20  ft.  6  in.  All  of 
them  were  going  at  a  moderate  rate.  The  numbers,  and  correspond- 
ing lines  on  the  ground,  indicate  spaces  of  one  foot ;  and  as  the  pho- 
tographs were  taken  in  succession  at  the  same  intervals,  they  will 
be  understood  to  show  the  position  of  the  limbs  at  each  interval  of 
one  foot.  The  position  of  the  camera  is  indicated  by  the  direct  line 
on  the  ground,  and  is  that  of  the  observer.  In  the  last  series  the 
gauge  line  shows  how  little  the  centre  of  gravity  is  deflected  in  its 
trajectory  from  a  direct  line,  and  this  line  will  be  found  to  vary  least 
when  the  speed  is  the  greatest.  By  the  aid  of  these  lines  and  their 
figures  the  reader  may  be  able  to  measure  the  strides  and  parts  of 
strides,  and  determine  their  respective  intervals. 

It  has  been  observed  that  there  is  not  perfect  regularity  in  the  line 
of  the  footprints  of  a  running  horse,  especially  if  the  ground  is  uneven. 
This  is  owing  to  the  variations  of  the  centre  of  gravity,  which  compel 
the  corresponding  variations  of  the  positions  of  the  small  base  which 
supports  it ;  through  an  instinct  of  the  same  kind  which  we  recognize 
in  ourselves,  and  make  use  of  when  we  fail  to  give  proper  attention  to 
the  ground  on  which  we  are  walking  and  govern  the  movements  of 
our  feet  accordingly.  This  we  do  not  always  do,  and  the  effect  is  to 
cause  us  to  stagger  even  when  we  are  sober.  This  instinct  must  be 
regarded  as  existing  in  a  higher  degree  in  a  horse,  as  his  locomotive 
apparatus  is  more  complicated  and  of  a  higher  order  than  that  of  man. 

If  the  reader  is  interested  in  knowing  how  far  this  law  of  the  mech- 
anism of  running  holds,  he  may  follow  it  in  the  succeeding  plates. 
He  will  see  the  same  movement  in  the  greyhound,  Plates  XVIII., 
XIX.,  and  in  Plate  XX.  two  hounds  running  at  unequal  rates  of 
speed.  It  is  the  same  in  the  ox  running,  Plate  XXL,  and  has  been 
proved  true  of  the  goat,  and  will  be  found  to  hold  true  of  all  those 
quadrupeds  whose  four  limbs  are  of  like  proportions. 


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THE    HORSE    IN    MOTION.  99 

There  is  another  class  of  quadrupeds,  whose  posterior  extremities 
are  developed  to  a  much  greater  degree  than  the  anterior  ones,  and 
their  mode  of  progression  varies  more  or  less  from  the  theory  of  motion 
as  given  in  the  preceding  pages.  The  only  one  of  this  class  of  whose 
stride  \ve  are  able  to  present  an  analysis  is  the  deer.  In  this  animal 
the  same  order  of  succession  of  the  feet  may  be  observed ;  but,  at  the 
moment  when  it  might  be  expected  that  he  would,  as  in  the  horse,  rise 
from  one  of  the  fore  legs,  owing  to  its  feebleness  he  fails  to  do  so,  but 
the  hind  legs  are  thrust  forward  to  the  ground,  one  of  them  in  advance 
of  the  fore  foot  and  the  centre  of  gravity,  and,  while  one  of  the  fore 
legs  still  supports  the  weight  of  the  anterior  part  of  the  body,  by  the 
combined  action  of  the  posterior  extremities  he  projects  himself  by 
a  bound,  and  alights,  not  upon  one  of  the  hind  feet,  but  upon  one  of 
the  anterior  extremities ;  but  the  action  of  the  limbs  in  pairs  is  not 
synchronous,  one  of  them  being  a  pace  in  advance  of  the  other,  to  dis- 
tribute the  shock.  This  mode  of  progression  the  deer  is  able  to  per- 
form by  reason  of  the  length  and  angles  of  the  bones  of  his  limbs 
and  the  lightness  of  his  body,  and  it  is  adapted  to  the  nature  of  the 
ground  among  the  hills  where  he  finds  his  only  safety,  and  where 
the  horse  would  be  at  as  great  a  disadvantage  as  the  deer  is  upon  the 
plain.  For  reasons  already  stated,  it  is  not  possible  to  sustain  this 
gait  for  a  long  time  from  the  exhaustion  which  it  produces.  The 
action  of  the  horse  in  leaping  will  be  reserved  for  another  chapter. 

From  the  knowledge  we  have  gained,  by  the  use  of  instantaneous 
photography,  as  to  the  action  of  the  feet  in  running,  the  answer  to  the 
questions  propounded  by  William  Percivall  thirty  years  ago  is  obvious: 
"  What  is  the  reason  why  the  flexor  tendons  fail  so  much  more  fre- 
quently than  others  ?  Another,  Why  those  of  the  fore  limb  should 
fail  rather  than  the  flexor  tendons  of  the  hind  leg."  * 

In  the  following  quotation  he  gives  the  answer  to  his  own  question, 
in  accordance  with  the  heretofore  accepted  theory  of  the  run.  "  I 
have  more  than  once  had  occasion  to  direct  attention  to  the  important 
functions  performed  by  the  hind  limbs  in  the  acts  of  progression,  and 
to  contrast  these  with  the  comparatively  light  duties  of  the  fore  limbs. 

•  Hippopathology,  Vol.  IV.  p.  346. 


100  THE   HORSE   IN    MOTION. 

While  the  former,  like  a  pair  of  oars  at  work  in  a  boat,  are  plying  for- 
wards and  backwards,  forcing  the  body  onward,  the  latter,  more  like 
stilts,  are  employed  in  sustaining  the  propelling  parts,  lest  the  body  fall 
forward  to  the  ground.  I  have  likewise  afore  observed,  that  two  such 
different  functions  necessarily  distress  different  parts  of  the  limbs, — 
the  hock  being  the  part  most  exerted  in  the  hind,  the  feet  and  legs  the 
parts  most  tried  in  the  fore  limbs.  What  distresses  the  sinews  of  the 
fore  limbs  so  much  is  the  extreme  distension,  almost  preternatural,  to 
which  these  legs  are  put  in  hard  galloping  and  leaping  every  time  the 
weight  of  the  body  descends  upon  them,  at  a  moment  when  they  are 
stretched  out  to  their  utmost,  as  they  must  be,  to  receive  it ;  and  it  is 
to  this  identical  position  of  the  limb,  whenever  any  weight  or  force 
of  extraordinary  amount,  or  in  any  sudden  or  unexpected  manner, 
descends  upon  it,  that  strain  or  sprain  is  produced."  * 

It  is  now  perfectly  clear  that  it  is  in  their  action  as  propellers 
that  the  flexors  of  the  fore  leg  become  injured  in  their  tendons,  and 
in  the  position  shown  in  Fig.  12;  though  there  is  little  doubt  that 
if  the  weight  of  the  rider  were  not  superimposed  to  that  of  the  horse, 
this  accident  would  rarely  happen.  Sprains  involving  the  ligaments 
of  the  joints  may  occur  at  any  time  when  the  foot  from  any  cause  is 
not  set  squarely  upon  the  ground,  but  this  is  an  accident  of  quite  a 
different  nature  from  that  to  which  reference  is  made  above. 

We  have  designated  the  pace  under  consideration  as  the  run, — 
the  pace  used  in  racing,  or  the  fastest  known  to  the  horse  and  other 
domestic  animals.  What,  then,  is  the  gallop  ?  If  we  are  to  be  con- 
fined to  the  definition  of  the  gallop  given  in  the  dictionaries,  and 
generally  accepted  by  all  writers  on  the  horse,  we  are  forced  to  the 
conclusion  that  there  is  no  such  pace,  that  it  is  a  fiction.  Webster 
defines  the  gallop  as  "  a  mode  of  progression  by  quadrupeds,  par- 
ticularly by  a  horse,  by  lifting  alternately  the  fore  feet  and  the  hind 
feet  together,  in  successive  leaps  or  bounds " ;  and  Worcester,  "  to 
move  forward  as  a  horse  by  such  leaps  that  the  hind  legs  rise  before 
the  fore  legs  quite  reach  the  ground."  That  the  pace  which  we  call 
the  run  is  not  such  as  will  bear  the  definition  given  is  very  clear. 

*  Hippopathology,  Vol.  IV.  p.  346. 


THE    HORSE    IN    MOTION.  IOI 

The  camera  has,  under  the  direction  of  Mr.  Stanford,  been  made  to 
analyze  all  the  paces,  and  none  has  been  discovered  that  answers  to  it ; 
yet  it  is  to  this  pace  that  the  term  "gallop"  has  been  always  applied. 

When,  three  or  four  years  ago,  the  results  of  Mr.  Stanford's  experi- 
ments with  twelve  cameras  were  distributed  in  art  circles,  the  photo- 
graphs sent  met  everywhere  with  surprise  and  incredulity,  and  in  some 
quarters  with  ridicule  and  burlesque.  Such  result  ought  to  have  been 
expected.  They  were  not  understood,  and  the  revelation  was  so  an- 
listic  to  all  received  opinions  from  the  earliest  times,  that  one 
could  not  help  but  laugh  ;  and  that  they  do  not  understand  them 
now  does  not  surprise  us,  for  hippo-anatomy  has  been  always  taught 
under  the  light  of  a  false  hypothesis.  When  we  consider  how  little 
the  simple  movements  of  the  trot  were  understood  by  the  most  learned 
of  the  teachers  of  animal  motion,  is  it  a  matter  of  wonder  that  the 
complicated  mechanism  of  the  run  had  been  kept  so  profound  a  secret 
in  the  open  face  of  day  from  time  immemorial  ? 

A  revelation  so  startling  as  that  made  by  the  camera  carried  results 
too  far-reaching  and  revolutionary  to  be  at  once  accepted,  though  it 
came  direct  from  heaven.  There  is  too  much  capital  invested  in 
works  of  art  all  over  the  civilized  world  to  permit  the  innovation 
without  protest,  and  ridicule  is  the  cheapest  argument  that  can  be 
employed  in  controversy,  for  it  does  not  require  truth  for  its  founda- 
tion, and  but  a  low  order  of  talent  for  its  display. 

All  artists  know  the  value  of  the  horse  as  a  chef  d'ceuv re,  and  he 
is  made,  next  to  the  human  figure,  the  first  subject  in  elementary 
studies  in  art ;  but  from  what  source  have  been  derived  all  the  models 
of  horses  in  motion  ?  Who  does  not  tire  in  looking  over  the  monot- 
onous repetition  of  outstretched  legs,  as  if  their  bearers  had  been  shot 
from  a  cross-bow,  and  were  moving  at  a  mark  without  any  agency  of 
their  own,  and  when  the  slightest  variation  of  that  inflexible  form 
would  spoil  the  pose  and  ruin  a  picture.  We  are  told  that  the  object 
is  to  represent  action.  \Yould  not  that  object  be  more  readily  attained 
if  some  position  were  represented  that  is  known  to  be  true,  instead  of 
one  that  is  proved  to  be  impossible  ?  "  But  art  must  represent  things 
as  they  seem,"  says  an  objector.  Those  who  think  they  see  a  horse  in 


102  THE   HORSE    IN   MOTION. 

the  positions  given  in  the  conventional  way  have  their  conceptions 
formed  by  a  false  hypothesis;  those'  who  are  initiated  into  the  true 
theory  of  the  movement  experience  no  difficulty  in  perceiving  the 
movements  of  the  limbs  in  precisely  the  manner  represented  in  the 
plates  here  given,  and  wonder  they  never  saw  them  so  before.  One 
will  recognize  this  movement  more  readily  in  a  dog  running  than  in 
a  horse. 

Some  of  these  positions  seem  grotesque,  but  for  no  other  reason 
than  because  the  action  is  not  understood.  When  it  is  so,  they  will 
appear  as  necessary  progressive  stages  in  a  never  varying  series  of 
movements,  the  result  of  which  is  locomotion,  and  it  will  appear  that 
it  cannot  be  performed  without  them ;  the  eye  that  understands  them 
can  never  be  deceived,  and  the  slightest  deviation  from  the  law  of  their 
co-ordination  will  instantly  be  detected  in  a  silhouette  as  surely  as  the 
animal  would  be  to  suffer  the  consequences  of  a  misstep. 

Quadrupeds  will  be  recognized  as  being  possessed  of  locomotive 
machinery,  self-moving,  with  all  the  parts  acting  in  perfect  harmony, 
and  not  passive  projectiles.  If  Art  is  the  interpreter  of  nature,  as  is 
claimed,  she  is  false  to  her  mission  when  she  wilfully  persists  in  per- 
petuating a  falsehood.  But  in  this  case  she  cannot  if  she  would. 
Once  attention  is  called  to  the  true  theory  of  quadrupedal  motion, 
the  truth  of  each  one  of  these  positions,  and  the  interpretation  of  them 
in  relation  to  progression,  is  so  quickly  recognized,  while  the  error  of 
the  old  theory  of  the  gallop  becomes  so  manifest,  that  artists  will  no 
more  be  able  to  claim  that  they  represent  nature  as  she  seems,  when 
they  depict  a  horse  in  full  run  in  the  conventional  manner,  or  the 
mythical  gallop. 

Plates  XXV.  and  XXVI.  represent  sketches  taken  from  elemen- 
tary drawing-books  manufactured  in  London  and  Berlin  and  used  in 
the  schools.  They  are  heliotyped,  on  a  reduced  scale,  in  order  that 
there  shall  be  no  suspicion  of  inaccuracy  in  the  copies. 

After  what  has  been  said,  comment  is  unnecessary ;  but  I  would 
ask,  if  animal  motion  is  to  be  always  taught  to  follow  such  severely 
false  models,  wherein  is  it  better  teaching  than  that  of  the  priests  of 
Osiris,  with  whom  all  forms  were  .stereotyped  for  thousands  of  years, 


CONVENTIONAL    POSITIOJS   OF   QUADRUPEDS  IN  MOTION 


PL, 


COTSiVETSTTlOtTAL    POSITIONS   Of  QUADRUPEDS  IN 


THE    HORSE    IN    MOTION.  IO3 

and  the  last  stages  of  their  art  were  worse  than  the  first  ?  And  here 
1  would  diverge  still  farther  from  the  path  I  had  marked  out  for 
myself,  to  protest  against  the  soundness  of  that  dogma  that  art  should 
represent  things  as  they  seem.  I  will  not  enter  upon  a  discussion  of 
the  general  proposition,  it  would  carry  me  far  beyond  the  special 
subject  of  this  essay;  but  I  will  limit  myself  to  the  consideration 
of  the  proposition  as  it  is  applied  to  the  representations  of  the  move- 
ments of  the  limbs  of  the  horse  in  motion.  I  am  often  told  that 
we  do  not  represent  the  spokes  of  a  carriage -wheel  in  motion  as  dis- 
tinct spokes,  but  they  are  made  to  run  together  as  they  really  appear 
to  the  eye,  where  new  images  are  made  upon  the  retina  before  the 
first  are  lost.  Lightning  is  represented  as  a  zigzag  line,  when  in 
reality  it  is  a  spark ;  but  this  spark  moves  with  such  inconceivable 
rapidity  that  it  is  quite  impossible  to  calculate  the  time  of  its  passage. 
The  track  of  the  electric  spark  is  unquestionable,  and  when  that  is 
represented  there  is  no  untruth :  it  would  be  impossible  to  represent 
lightning  in  any  other  way.  Lightning  is  not  only  the  spark,  but 
the  track  it  describes  in  the  sky  also.  To  represent  them  thus  is 
to  represent  the  actual  truth,  and  so  it  expresses  action,  and  no  error 
is  inculcated.  But  does  one  ever  represent  the  horse's  legs  in  that 
manner  to  express  their  action  ?  Why  not  ?  If  it  cannot  be  done, 
why  assume  a  false  and  hackneyed  position  that  cannot  be  true  ? 
Why  must  every  equestrian  statue  in  Europe  follow  the  model  of  the 
Antique  Balbi  in  the  Neapolitan  Museum,  with  the  bones  of  the  fore 
leg  flexed  at  right  angles,  and  the  other  three  feet  upon  the  ground  ? 
No  such  position  was  ever  true,  nor  can  it  seem  to  be  so  to  any  one 
who  gets  his  impressions  from  nature. 

The  theory  of  the  run  and  the  mechanism  of  the  locomotive 
apparatus  of  the  horse  will  soon  be  common  property  among  admirers 
of  the  animal ;  and  when  that  knowledge  becomes  general,  all  the 
famous  paintings  in  which  he  is  a  prominent  figure  in  the  "  gallop " 
will  be  relegated  to  the  museums  as  examples  of  old  masters,  to 
illustrate  the  progressive  stages  in  the  development  of  art. 

If  the  theory  of  the  run  is  understood,  the  action  in  the  canter  will 
present  no  difficulty ;  for  the  theory  is  the  same  in  both,  and  the  varia- 


104 


THE    HORSE   IN    MOTION. 


tions  in  the  order  of  movement  of  the  feet  are  changes  rendered  neces- 
sary by  the  low  rate  of  speed  in  the  latter.  In  Fig.  i,  Plate  XXVII.,  the 
cantering  horse  is  seen  in  the  act  of  leaving  the  ground  with  one  fore 
foot  as  in  the  run,  and  his  feet  are  clear  of  the  ground  only  for  the  dis- 
tance of  two  feet  and  five  inches,  as  indicated  by  the  lines  on  the  ground, 
when  the  diagonal  hind  foot  comes  to  the  support  of  gravity,  not  under 
its  centre,  as  in  the  run,  but  behind  it  (see  Fig.  4),  and  therefore  cannot 
prevent  the  body  from  falling  forward.  In  order  to  prevent  this  result, 
it  is  necessary  that  one  of  the  fore  feet  should  support  it,  and  it  is 
always  that  fore  foot  which  is  diagonal  to  the  hind  one  that  is  upon  the 
ground.  The  other  hind  foot  follows  at  the  usual  distance  from  its  fel- 
low. He  has  now,  through  three  Figures,  three  feet  upon  the  ground,  as 
in  the  walk,  after  which  the  order  of  the  run  is  resumed.  Fig.  1 1  nearly 
corresponds  to  Fig.  i  ;  the  difference  observed  is  owing  to  a  want  of  cor- 
respondence in  the  time  of  exposure  of  the  sensitive  plate  of  the  camera. 
In  Fig.  i  the  fore  leg  has  given  its  quick  thrust,  and  the  knee  is  slightly 
bent  as  it  is  about  to  leave  the  ground,  while  in  Fig.  1 1  it  is  still  acting 
as  supporter  and  propeller. 

It  is  clear  that  if  the  animal  moved  with  more  will  and  greater  speed, 
planting  his  hind  foot  farther  forward  in  support  of  the  centre  of  gravity, 
there  would  have  been  no  necessity  for  the  fore  leg  to  have  performed 
that  office ;  and  the  pace  would  not  have  differed  from  the  run.  The 
length  of  time  during  which  three  feet  support  the  body  gives  time  for 
the  rider  to  settle  in  the  saddle,  and  causes  that  easy  cradle-motion 
which  makes  it  a  favorite  gait  with  ladies. 


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CHAPTER  VI. 

THE  LEAP  NOT  PROPERLY  A  PACE. — ACTION  IN  THE  LEAP  DESCRIBED.  —  THE  DANGER 
TO  BE  APPREHENDED  IN  THE  LEAP.  —  THE  STANDING  LEAP.  —  CORRESPONDENCE  IN 
THE  ACTION  OF  THE  HORSE  IN  THE  LEAP  AND  THE  DEER  IN  THE  BOUND.  —  ACTION 
IN  THE  TROT.  —  DISTINCTION  BETWEEN  A  STEP  AND  A  STRIDE.  —  THE  DIFFICULTY 
TO  BE  ENCOUNTERED  IN  INCREASING  THE  SPEED  OF  TROTTERS.  —  DIFFERENCE  IN 
THE  ACTION  IN  THE  TROT  AND  THE  RUN. — DIFFICULTY  IN  RESTRAINING  A  HORSE 
FROM  BREAKING  INTO  A  RUN  EXPLAINED.  —  FAST  TROTTING  CULTIVATED  IN  AMERICA 
IN  THOROUGHBREDS. — TROTTING  NOT  HEREDITARY,  BUT  A  HABIT.  —  THEORY  AND 
MECHANICAL  ACTION  IN  THE  TROT.  —  THE  ACTION  IN  AMBLING,  OR  "PACING."  — 
DEFINITION  OF  THE  WALK  APPLICABLE  TO  BIPEDS,  NOT  TO  QUADRUPEDS.  —  THE 
ACTION  IN  THE  WALK.  —  THE  ACTION  IN  THE  PACE  KNOWN  AS  SINGLE-FOOT. 

THE  leap  cannot  be  properly  considered  as  a  pace ;  although  it  is  a 
mode  of  progression,  it  is  not  a  continuous  one.  Before  any  quadruped 
will  venture  to  undertake  it,  he  must  have  acquired  a  considerable 
degree  of  experience  in  locomotion,  and  that  confidence  in  the  use  of 
his  limbs  which  experience  only  can  give.  That  it  is  naturally 
acquired,  there  cannot  be  a  doubt,  as  it  is  necessary  to  all  quadrupeds 
in  a  wild  state  to  enable  them  to  overcome  obstructions  otherwise 
insurmountable.  The  weight  of  the  horse's  body,  however,  renders  it 
necessary  for  him  to  reduce  his  speed,  and  with  it  his  momentum, 
before  he  can  safely  attempt  it,  even  when  the  obstruction  is  of  mod- 
erate height.  It  is  a  feat  in  which  he  is  excelled  by  most  quadrupeds, 
all  the  quadrumana,  and  even  by  man  himself. 

I'rom  the  mode  of  action  of  the  various  parts  of  the  locomotive 
machinery,  as  shown  in  Chapters  IV.  and  V.;  the  reader  will  experience 
little  difficulty  in  understanding  what  takes  place  in  the  leap.  The 
action  is  so  full  of  interest  that  we  have  given  a  number  of  illustrations 
to  enable  the  reader  to  observe  the  many  different  phases  the  leap 

14 


io6 


THE    HORSE    IN    MOTION. 


presents.  All  the  plates  show  the  horses  approaching  the  barrier  at  a 
run  ;  but  no  sooner  is  it  observed  than  they  begin  to  shorten  their  steps 
and  apparently  measure  its  distance.  In  Plate  XXVIII.  the  hurdle  is 
placed  at  an  elevation  of  three  feet  six  inches,  and  the  horse  betrays 
his  anxiety  by  shortening  his  paces,  and  advancing  with  both  hind  feet 
nearly  simultaneously  and  alternately  with  one  fore  foot,  or  what  is 
called  prancing,  until  he  has  approached  the  barrier  sufficiently  near 
to  satisfy  himself  that  he  can  surmount  it,  when  he  plants  his  hind  feet 
well  under  the  centre  of  gravity,  and  instantly  the  fore  leg  resting  upon 
the  ground  gives  the  thrust  explained  in  Chapter  IV.,  by  which  the 
anterior  portion  of  the  body  is  raised,  and  the  action  is  immediately 
followed  by  all  the  muscles  of  the  haunch,  which  project  the  body  to 
the  required  height.  The  anxiety  and  want  of  confidence  of  the 
animal  are  betrayed  by  the  nearness  of  his  approach  to  the  obstacle 
and  the  arrest  of  his  momentum  before  he  ventures  the  leap.  By 
the  arrest  of  his  momentum  he  has  diminished  the  danger  of  injury 
to  the  back  tendons  on  reaching  the  ground  again. 

In  Plate  XXIX.  we  see  the  same  horse  under  somewhat  altered 
conditions.  The  hurdle  is  six  inches  lower,  and  he  advances  with 
increased  confidence,  leaving  the  ground  eleven  feet  from  it. 

The  relations  of  the  levers,  or  passive  parts  of  the  machine,  in  the  act 
of  leaving  the  ground  in  leaping,  are  shown  in  Plate  XXXV.  Fig.  i, 
where  the  positions  of  the  posterior  extremity  are  the  extreme  of 
extension. 

The  next  plate  represents  a  full  series  of  views  by  twenty-four  cam- 
eras, by  means  of  which  the  movements  in  leaping  are  carried  four  feet 
farther.  The  posterior  extremities  from  the  extreme  of  extension,  on 
leaving  the  ground,  pass  to  the  opposite  extreme  of  flexion  as  they  pass 
the  barrier,  and  both  the  posterior  and  anterior  limbs,  as  they  pass  suc- 
cessively in  pairs,  are  so  nearly  in  unison  that  they  seem  in  the  silhou- 
ette to  coincide.  Plate  XXXII.  shows  the  same  horse  as  seen  in  the 
last  preceding  plate,  after  he  has  passed  the  hurdle  and  is  nearing  the 
ground.  The  anterior  extremities,  that  coincided  in  passing  the  hurdle, 
are  now  separating  in  order  that  they  shall  not  make  contact  with  the 
ground  at  the  same  time.  One  of  the  fore  legs  is  extended  as  in  the 


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TIIK  HOKSI-:  ix  MOTION.  107 

run,  to  check  the  force  of  the  descent,  which,  from  the  loss  of  hori- 
zontal momentum,  has  little  more  than  the  momentum  of  gravity  to 
deal  with.  This  is  the  moment  of  extreme  clanger  to  the  pastern  joint 
and  flexor  tendons;  but  before  these  parts  are  put  to  the  extreme  test 
the  other  fore  leg  comes  to  the  relief  of  its  fellow,  and  immediately 
after  the  posterior  extremities,  one  after  the  other,  are  planted  under 
the  centre  of  gravity,  and  by  their  great  lifting  force  relieve  the  ante- 
rior extremities,  and  all  the  limbs  are  free  to  act  their  various  parts  in 
the  run,  which  is  not  fairly  resumed  in  this  series,  the  velocity  at 
no  time  being  sufficient  to  enable  the  animal  to  clear  the  ground. 
The  action  after  the  leap  may  be  still  further  traced  in  Plate  XXXIII. 
where  the  run  is  not  yet  fully  resumed,  the  speed  being  only  equal  to 
the  disposition  of  the  limbs  as  in  the  canter,  the  order  being  the  same 
as  in  the  run.  The  last  illustration  of  the  leap  that  we  offer  is  very 
curious.  The  horse  was  very  reluctant  to  perform  the  leap  required  of 
him,  and  came  to  a  standstill  immediately  in  front  of  the  hurdle,  and 
only  after  great  urging  did  he  attempt  to  surmount  it.  The  action  of 
the  locomotive  organs  is  shown  to  be  the  same  in  this  as  in  the  other 
series  representing  the  leap,  only  with  less  courage  manifested ;  and 
there  is  little  danger  in  its  execution.  As  the  horse  lost  his  horizontal 
momentum  before  leaping,  so  he  had  none  when  he  reached  the  ground 
on  his  descent.  It  should  be  observed  that  in  all  these  series  the 
intervals  between  the  successive  pictures  are  those  of  space  and  not  of 
lime,  as  the  horse  makes  his  own  pictures  in  a  manner  that  will  be 
fully  explained  in  the  Appendix.  The  intervals  in  all  the  series  of 
twenty-four  pictures  represent  distances  of  one  foot  in  a  horizontal 
direction.  Fig.  2,  Plate  XXXV.,  shows  the  position  of  the  skeleton 
as  the  animal  meets  the  contact  with  the  earth.  By  means  of  these 
skeleton  views  the  reader  is  enabled  to  build  up  the  entire  loco- 
motive apparatus  with  the  aid  of  the  anatomical  plates,  and  satisfy  him- 
self as  to  the  forces  that  are  employed  in  producing  the  movements. 

On  reference  to  Plates  XXIII.  and  XXIV.,  it  will  be  perceived  how 
great  is  the  correspondence  in  the  action  of  the  deer  in  bounding  and 
the  horse  in  leaping.  In  both  the  action  on  leaving  the  ground  is 
the  same.  When  the  hind  feet  are  upon  the  ground,  well  under  the 


I08  THE   HORSE    IN    MOTION. 

centre  of  gravity,  the  spring  of  one  fore  leg  lifts  the  anterior  half 
the  body,  and,  the  action  of  the  posterior  extremities  immediately  fol- 
lowing, the  whole  body  is  projected  into  the  air;  but,  the  deer  being  in 
more  rapid  motion,  his  feet  take  the  ground  at  longer  intervals  and 
more  regular  order,  and  so  diminish  the  danger  of  stumbling,  as  well 
as  distribute  the  shock  of  contact  and  equalize  the  support  of  the 
weight  of  the  body. 

When  the  horse  reduces  his  speed  in  running  so  that  he  can  no  longer 
maintain  his  balance  upon  one  foot,  he  will  usually  drop  into  a  trot,  which 
is  a  gait  having  two  feet  as  bases  of  support  instead  of  one.  The  theory 
of  the  trot  is  the  same  as  that  of  the  walk,  but  adapted  to  a  higher  rate 
of  speed.  It  differs  from  a  walk  in  that  the  latter  has  always  two  feet 
upon  the  ground,  while  in  the  trot  there  is  always  a  space  of  time,  of 
greater  or  less  amount,  in  which  all  the  feet  are  off  the  ground.  Other 
differences  will  be  noticed  when  we  come  to  analyze  the  walk.  They 
correspond  in  that  the  weight  of  the  body  is  borne  by  the  diagonal 
extremities  alternately,  and  in  the  general  co-relation  of  the  limbs  in 
their  mechanical  action.  The  action  in  the  trot  is  the  more  vigorous 
as  the  distance  in  which  the  body  moves  unsupported  is  increased. 
The  definition  of  the  word  step  in  its  general  use  is  somewhat 
ambiguous.  It  is  often  used  synonymously  with  stride.  In  the  step 
of  both  quadrupeds  and  bipeds  it  is  understood  to  mean  the  distance 
spanned  by  the  two  feet  both  resting  on  the  ground.  This  will  vary 
with  the  muscular  energy,  but  is  limited  by  anatomical  proportions. 

The  stride  is  here  used  to  signify  the  distance  passed  over  by  one 
foot  from  the  time  it  leaves  the  ground  until  it  reaches  it  again, 
measured  to  corresponding  points,  and  is  equal  to  two  steps ;  but  in 
the  trot  this  definition  will  not  hold  good,  for  there  must  be  added  a 
certain  distance,  differing  according  to  speed,  in  which  neither  of  the 
feet  will  be  on  the  ground.  If  a  represents  the  step  in  the  walk,  and 
x  the  distance  passed  over  by  the  foot  after  the  other  foot  is  raised, 
the  step  in  the  trot  would  be  expressed  by  a  +  x,  and  when  a 
constant,  the  step  will  vary  as  x.  In  the  run,  there  being  four  steps, 
and  an  interval  when  all  the  feet  are  off  the  ground  equal  to  a  step, 
the  stride  would  be  expressed  by  5  a.  The  stride  is  divided  in  the 


THE   HORSE   IN   MOTION.  109 

trot  into  two  periods  by  the  alternate    feet,  so  that    in   the  trot  the 
horse  is  twice  clear  of  the  ground  in  each  stride.     The  step  being  sup- 

1  to  be  a  constant  quantity  in  the  fast  trot,  the  stride  can  be  ex- 
tended only  by  increasing  the  space  which  the  body  passes  over  with 

ntre  of  gravity  unsupported.  \Yhile  in  the  slow  or  jog  trot  this 
distance  is  small,  in  the  flying  trot  it  exceeds  that  in  which  the  body  is 
supported,  and  hence  arises  the  great  difficulty  in  attaining  a  high  rate 
of  speed.  As  was  stated  in  the  preceding  chapter,  the  law  of  falling 
bodies  increases  the  difficulty  in  locomotion  in  the  ratio  of  the  square 
of  the  time  in  which  the  body  is  so  unsupported.  It  becomes  a  ques- 
tion of  power  of  resistance,  or  strength  of  the  parts  on  which  that 

:.mce  depends.  On  the  other  hand,  the  strength  of  the  parts,  as 
the  joints,  bones,  ligaments,  and  tendons,  involves  increase  of  weight, 
which  is  incompatible  with  rapidity  of  movement,  without  a  corre- 
sponding increase  of  power  of  the  muscles  and  weight  of  the  body  to 
he  borne,  so  that  the  limits  of  speed  attainable  in  a  trot  are  reached 
more  rapidly  than  in  a  run,  in  which  the  limit  is  to  be  found  in  the 
measure  of  activity. 

In  the  run  the  stride  is  divided  into  five  parts,  instead  of  two,  as  in 
the  trot,  each  limb  taking  its  turn  as  supporter  and  propeller,  with  a 
scarcely  appreciable  interval  between,  and  an  interval  between  the  last 
fore  leg  and  the  first  hind  one  representing  a  fifth  of  the  whole  stride. 
Each  limb,  therefore,  works  one  fifth  of  each  stride  and  rests  the  other 
four  fifths.  The  longest  stride  given  of  the  run,  in  the  examples  fur- 
nished, is  that  of  "  Florence  A."  (Plate  XVII  ),  where  it  is  given  at 
twenty  feet  six  inches,  or  a  little  more  than  four  feet  as  the  portion 

;ned  to  each  limb.  It  will  be  observed  that  in  the  trotting  horse 
(Plate  XXXVI.),  whose  stride  is  given  at  eighteen  feet  three  inches, 
the  time  of  support  by  two  limbs  is  about  the  same,  while  the  time  in 
which  there  is  no  support  given  is  greater,  and  divided  into  two  inter- 
vals. So  in  Plate  XL.  the  gravity  is  supported  about  half  the  time  by 
limbs,  and  the  other  half  by  none,  alternating  every  four  feet. 
Notwithstanding  the  wonderful  mechanical  provision  in  each  of  the 
four  limbs  to  secure  uniform  support  and  propulsion  while  the  feet  rest 
upon  the  ground,  the  instant  that  the  body  ceases  to  be  supported  it 


110  THE   HORSE   IN   MOTION. 

becomes  subject  to  the  law  of  the  descent  of  falling  bodies  and  all  its 
consequences,  as  mentioned  in  the  last  chapter,  and  the  greater  the 
speed  of  the  animal  the  more  serious  the  possible  consequences ;  and 
though  no  small  advantage  is  gained  by  relieving  the  horse  of  the 
weight  of  the  rider,  and  placing  it  upon  a  sulky,  it  is  the  cause  of 
serious  damage  to  the  finest  stock.  It  is  no  small  accomplishment 
in  a  horse,  however  thoroughbred,  to  be  so  well  disciplined  that  he 
will  not  break  from  a  fast  trot,  however  goaded  by  his  driver  and  his 
own  ambition  in  a  sharp  contest,  into  a  pace  in  which  he  is  conscious 
he  can  make  better  time  with  far  more  ease  than  in  the  one  he  is 
forced  to  take. 

The  trot  appears  from  our  analysis  not  to  have  been  designed  as  the 
fastest  gait,  but  for  the  medium  one  between  the  run  and  the  walk,  and 
when  not  urged  too  far  beyond  his  supports;  it  is  the  strong  business 
gait,  in  which  he  is  capable  of  travelling  farther  in  a  day's  journey  with 
less  fatigue  than  any  other.  It  is  owing  to  this  fact  that  it  has  become 
the  favorite  pace  in  America,  and  has  been  cultivated  to  a  greater  ex- 
tent than  in  any  other  country ;  indeed,  we  fail  to  learn  anything  of  the 
trotting  horse  from  any  source  before  the  importation  of  "  Messenger," 
who  was  a  thoroughbred  running  horse,  and  manifested  extraordinary 
speed  in  the  trotting  pace  after  his  arrival  in  America.  It  is  very  diffi- 
cult to  discover  wherein  the  mechanical  proportions  and  points  for  a  fine 
runner  would  not  apply  equally  well  to  a  fast  trotter;  and  it  is  claimed 
that  there  has  been  no  fast  trotter  who  did  not  trace  his  pedigree  to 
thoroughbred  ancestry.  This  question,  however,  is  beyond  the  pale 
of  this  essay,  and  has  not  been  one  that  has  particularly  interested  us. 
It  will  be  difficult  for  one  to  believe  that  a  new  function  has  been  devel- 
oped in  the  time  that  has  elapsed  since  "  Messenger's  "  importation,  not 
yet  a  century,  even  by  the  most  advanced  Darwinian.  It  is  much  more 
reasonable  to  believe  that,  while  great  attention  has  been  paid  to  breed- 
ing those  qualities  that  insure  speed,  equally  great  care  has  been  be- 
stowed upon  training,  so  that  the  fast  horse  shall  display  his  powers  in 
the  trot  rather  than  in  the  run,  of  which  he  may  be  equally  capable. 
In  this  way  the  fast  trot  becomes  a  habit  with  the  individual,  and  in  i 
he  may  excel  his  powers  in  the  superior  gait.  But  the  habit  is  no 


THK    IIOKSK    IN    MOTION.  Ill 

heritcd,  nor  can  it  be  transmitted  to  descendants,  as  is  asserted  by  some 
authors.  Functions  and  faculties,  or  the  power  by  which  acts  are  per- 
formed and  habits  acquired,  may  be  inherited.  No  man  is  able  to  trans- 
mit to  his  off  sprint;  his  acquirements,  whether  of  mind  or  body.  The 
child  of  the  most  profound  scholar  will  not  know  one  letter  from  another 
until  he  is  taught  them,  and  will  learn  them  no  more  easily  for  all  his 
parent's  attainments.  Nascilur,  non  Jit  (horn,  not  made)  is  as  true 
in  this  sense  now  as  ever  it  was.  The  faculty  through  which  the 
parent  was  enabled  to  acquire  any  accomplishment,  whether  mental  or 
physical,  may  be  transmitted  to  offspring.  Even  these  are  not  congeni- 
tal or  coincident  with  birth,  as  the  function  of  breathing  is;  but  the 
tendency  is  inherited,  and  the  functions  will  be  developed  at  the 
proper  time,  and  in  the  order  that  their  exercise  will  be  required,  first 
for  the  existence,  protection,  and  development  of  the  individual,  then 
for  the  full  employment  of  all  the  powers  successively  with  which  it 

•mhnved  by  inheritance.  The  law  of  inherited  or  constitutional 
disease  is  the  same ;  all  are  not  congenital,  but  most  of  them  are 
developed,  like  consumption,  at  the  age  of  puberty,  and  others,  like 
cancer,  at  mature  life,  from  inherited  tendencies. 

When  the  colt  is  seen  soon  after  birth,  he  must  be  helped  upon  his 

and  the  first  efforts  of  his  long  and  feeble  limbs  are  to  walk,  in 
which  he  instinctively  obeys  the  law  to  alternate  the  limbs  and  so  pre- 

its  balance.  More  than  this  he  cannot  do.  Visit  him  a  few  days 
later,  and  he  will  be  found  not  only  able  to  walk  with  firmness,  but  to 
trot  away  from  your  approach.  When  you  next  visit  him,  after  a 

r  interval  of  time,  he  has  acquired  much  greater  control  of  his 
locomotive  organs,  and  he  will  move  off  in  a  trot  with  no  uncertain 
step,  and,  if  you  pursue,  he  will  break  into  a  run  (Plate  XLII.). 

The  last  pace  is  no  less  intuitive  than  the  first,  but  required  a 
longer  period  for  its  development.  It  is  an  acquired  pace,  but  not 
the  less  intuitive.  There  is  great  doubt  whether  the  complicated 
movement  of  the  run,  which  has  so  long  eluded  the  comprehension 
of  man,  was  ever  any  better  understood  by  the  most  sagacious  of  the 
quadrupeds  that  practised  it ;  and  the  identical  character  of  the  move- 
nent  through  so  many  species  of  them  shows  that  it  is  inherited,  or 


112  THE    HORSE    IN    MOTION. 

natural.  The  walk,  trot,  and  run  are  all  equally  natural,  and  each  is 
best  adapted  to  each  of  the  three  degrees  of  speed  which  the  animal 
finds  it  convenient  or  necessary  to  employ  in  his  feral  or  unbroken 
state. 

It  will  be  seen  that  the  theory  of  the  trot  is  the  same  as  that  in  the 
run,  namely,  that  the  centre  of  gravity  shall  be  supported  constantly 
and  propulsion  made  uniformly  by  all  the  extremities  from  the  lime 
they  reach  the  ground  until  they  leave  it,  but  by  two  alternate  limbs 
at  a  time,  and  not  by  one  as  in  the  run.  The  action  of  the  limbs  in 
shortening  and  extending,  to  enable  them  to  begin  the  support  early 
and  continue  it  late,  and  permit  the  centre  of  gravity  to  pass  over  them 
without  being  deflected,  is  the  same  in  both  paces.  The  action  is 
the  same,  differing  only  in  degree.  The  undulations  are  greatest  in 
the  slow  trot,  and  diminish  as  the  speed  is  increased.  Every  rider 
knows  this  from  experience ;  the  uncomfortable  trot  is  the  slow  one. 
The  reason  for  this  was  explained  when  treating  of  the  run  in  the  last 
chapter.  In  the  slow  trot  the  action  of  the  muscles  is  not  sustained, 
and  the  bony  levers  are  allowed  to  resume  their  normal  angles.  At 
each  half-stride  the  centre  of  gravity  regains  nearly,  if  not  quite,  its 
elevation  ;  but  as  the  horse  increases  his  speed  he  lowers  the  centre  of 
gravity,  and,  in  so  doing,  enables  the  extremities  to  reach  farther  and 
sustain  the  weight  longer,  while  the  rapidity  of  the  movement  of  the 
body  gives  it  a  momentum  that  forces  the  suspensory  ligament  to  yield 
and  the  angles  to  close  to  the  requisite  degree  to  prevent  the  alternative 
of  deflection  of  the  trajectory,  or  crushing  of  the  limb ;  and  if  measure- 
ments be  taken  of  the  height  of  the  horse  at  different  portions  of 
the  stride,  it  will  be  found  that  it  is  least  when  it  would  seem  that 
it  should  be  the  greatest,  that  is,  when  it  passes  the  perpendicular,  or 
that  point  where  the  supporting  limbs  are  shortest,  as  was  shown  in 
the  last  chapter  when  analyzing  the  action  in  the  run. 

While  the  action  of  the  limbs  in  the  two  paces  is  similar,  the  co- 
ordination of  them  presents  some  interesting  points  for  consideration. 
Instead  of  the  great  impulse  being  given  by  the  fore  leg,  as  in  the 
run,  it  acts  in  a  lesser  degree,  raising  the  centre  of  gravity  only  so  far 
as  to  give  its  co-operating  posterior  extremity  an  opportunity  to  use  its 


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•nil-:  iioKsr.  IN   MOTION.  113 

propelling  power  in  the  direction  of  the  centre  of  gravity,  as  in  Un- 
bound of  the  deer  and  the  leap  of  the  horse ;  for  if  it  were  given 
above  it  the  animal  would  be  pitched  headlong.  The  hind  foot  should 
be  the  last  to  leave  the  ground  on  a  priori  reasoning  ;  and  on  consulting 
the  silhouettes  of  the  trotting  horse  (Plates  XXXVI. -XL.),  such  will 
h  •  found  to  be  the  fact.  The  early  start  of  the  fore  foot  enables  it  to 
clear  the  way  for  the  hind  one  on  the  same  side  to  advance  to  the 
support  of  the  centre  of  gravity  in  its  turn  without  being  hit  by  it,  or 
overreached,  as  it  is  technically  called.  In  the  mean  time  the  fore 
foot,  having  a  more  circuitous  route  to  travel,  is  enabled  to  attain  its 
position  as  a  supporter  at  the  same  instant  as  its  co-operating 
partner. 

The  position  in  which  the  feet  fall  is  as  nearly  on  a  line  as  is  possi- 
ble without  their  interference,  both  in  the  trot  and  run,  as  may  be 
seen  by  referring  to  the  illustrations  of  the  paces  in  the  latter  part 
of  this  volume,  where  the  animals  are  seen  in  various  aspects  of  the 
same  position. 

Interference  with  the  posterior  feet  is  rendered  very  difficult  by  the 
mechanical  arrangement  of  the  hock  joint,  already  explained,  which 
causes  an  involuntary  circumduction  of  the  hind  feet  as  they  pass  each 
other,  and  yet  compels  the  feet  to  be  planted  successively  near  the 
same  base  line.  In  the  case  of  the  anterior  extremities  there  is  no 
corresponding  contrivance,  but  the  breadth  of  the  shoulders  renders  it 
unnecessary. 

For  obvious  reasons  it  is  not  possible  to  show  by  the  camera  the 
occurrence  of  interference,  but  overreaching  is  shown  in  Plate  XXXVI. 
Figs.  2,  10,  and  in  Plate  XXXIX.  Fig.  9.  The  fore  foot  being  dila- 
tory, or  the  disproportion  in  the  length  of  the  body  to  that  of  the  legs, 
exposes  the  fetlock  and  heel  to  injury  from  the  shoe  of  the  hind  foot ; 
but  generally  the  hind  foot  is  pushed  under  the  forward  one  as  the 
latter  rises. 

There  is  a  pace  closely  allied  to  the  trot,  and  differing  from  it 
only  in  one  particular,  and  that  is  that  the  limbs  do  not  move  diago- 
nally in  pairs,  but  those  on  the  same  side  move  together.  This  pace  is 
shown  in  Plate  XLIX.  Comparing  this  series  with  a  trotting  series 


114  THE    HORSE    IN    MOTION. 

(Plate  XXXVII.),  it  will  be  found  to  be  impossible  to  distinguish  one 
pace  from  the  other,  as  shown  in  the  silhouette.  This  pace  is  called 
racking,  or  pacing,  in  America,  and  ambling  in  England.  The  objec- 
tion to  the  name  pacing  is  that  the  word  pace  is  used  constantly  as  a 
general  term  for  all  the  different  modes  of  progression,  and  therefore 
leads  to  ambiguity.  While  in  the  trot  the  centre  of  gravity  falls  near 
the  intersection  of  the  two  straight  lines  drawn  through  the  diagonal 
footprints,  in  the  amble  it  is  shifted  from  side  to  side,  as  the  right  or 
left  feet  alternately  support  the  weight.  The  effect  of  this  is  to  give 
a  rolling  motion  to  the  body  like  that  of  a  ship  with  the  wind  abeam. 
It  is  an  easy  pace  for  the  rider,  being  free  from  the  sharp  undulations 
of  the  trot.  The  necessity  which  exists  of  rapidly  changing  the  base 
of  support  from  side  to  side  makes  it  practicable  in  the  horse  only 
when  the  speed  is  considerable,  and  quite  impossible  in  the  rate  pur- 
sued in  the  walk.  In  the  camelopard,  owing  to  the  shortness  of  his 
body  and  the  great  length  of  his  legs,  it  is  the  only  method  of  loco- 
motion possible,  as  he  would  overreach  in  the  paces  used  by  the  horse. 
He  is  able  to  make  progressive  motion  in  this  way  at  whatever  rate, 
from  the  great  elevation  of  the  centre  of  gravity,  and  the  consequent 
slow  oscillation  of  it ;  for  the  time  of  its  oscillation  increases  with  the 
length  of  the  line  from  the  centre  of  gravity  to  the  base  of  support. 

The  amble  is  natural  to  some  horses,  which  take  to  it  instead  of  the 
trot;  as  some  people  are  sinistrous,  though  the  greater  number  are 
dexterous  instinctively,  and  others  are  ambidexterous. 

Some  horses  are  amblers  first,  and  afterwards  learn  to  trot  and  travel 
equally  well  in  both  paces ;  indeed,  considering  the  small  proportion  of 
horses  that  fall  into  this  pace,,  and  the  record  made  by  them  on  the 
turf,  it  may  be  thought  to  have  no  disadvantage  over  the  regular  trot. 
It  would  seem  to  give  great  advantage  to  a  short-bodied  horse,  as  there 
is  no  danger  of  overreaching. 

Many  of  the  photographs  reproduced  in  the  photolithographs,  and 
used  in  this  volume  to  analyze  the  paces,  were  imperfect  in  lights  and 
shades,  and  others,  when  the  subjects  were  dark-colored,  were  in  sil- 
houette, to  which  all  were  reduced.  The  outlines  are  quite  perfect,  and 
the  details  in  other  respects  are  quite  unimportant  to  the  study  of  the 


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TFIK    MORSK    IN    MOTION.  115 

movements.  It  is  only  necessary,  in  order  to  determine  the  movements 
of  the  several  limbs,  to  suppose  either  of  them  to  be  right  or  left,  and 
follow  it  as  such  throughout  the  stride.  Examples  have  been  selected 
of  the  two  principal  paces,  when  the  horses  were  light-colored,  to 
reproduce  in  heliotype,  —  a  process  which  furnishes  an  exact  tran- 
script of  the  original  photograph  by  the  same  agency,  namely, 
the  sun. 

The  walk  is  the  simplest  of  the  paces,  and  best  understood.  It  is 
defined  to  be  that  pace  in  which  one  foot  is  not  raised  until  its  fellow 
is  upon  the  ground.  The  definition  is  as  applicable  to  quadrupeds  as 
to  bipeds,  if  in  the  former  we  assume  the  two  anterior  and  the  two 
posterior  extremities  as  pairs.  The  slow  walk,  or  saunter,  represents 
the  pendulum  of  writers  on  animal  mechanics,  by  whom  the  leg  was 
supposed  to  swing  like  a  pendulum  on  its  centre,  but  little  muscular 
force  being  used  except  to  counteract  the  attraction  of  gravity. 

A  man  in  walking  throws  the  centre  of  gravity  over  the  leg,  which 
is  to  serve,  for  the  moment,  as  a  column  of  support,  and  leans  forward 
until  the  centre  of  gravity  is  in  advance  of  the  foot  as  a  base  ;  this  ren- 
necessary  the  advance  of  the  other  foot  to  serve  as  a  new  base, 
and  the  action  of  the  flexor  muscles  upon  the  toes,  with  the  weight  of 
the  suspended  leg,  carries  the  centre  of  gravity  diagonally  forward  until 
it  is  again  supported  by  the  other  foot.  These  movements  are  all 
detailed  and  formulated  by  the  old  writers,  and  are  referred  to  here  for 
the  purpose  of  bringing  the  science  of  animal  dynamics,  as  it  has 
been  taught  until  now,  freshly  to  the  mind  of  the  reader. 

It  must  be  conceded  that  we  have  advanced  the  science  of  animal 
mechanics  somewhat  in  this  treatise,  and  demonstrated  the  fact  that 
its  problems  are  not  to  be  solved  by  physics,  as  heretofore  attempted, 
nor  yet  by  vital  force  exclusively ;  that  animal  motion  in  its  highest 
manifestation  is  the  resultant  of  both,  chiefly  of  vital  force,  but  neither 
can  be  ignored  by  one  who  would  understand  the  subject. 

Each  one  of  these  elementary  acts  of  progression  is  a  step,  and  a 
series  of  them  is  a  walk.  The  walk  of  a  quadruped  is  more  complex 
and  perfect  than  that  of  a  biped ;  for  while  the  latter  is  compelled  to 
oscillate  his  body  in  order  to  balance  it  upon  each  foot  alternately,  the 


Il6  THE    HORSE    IN    MOTION. 

quadruped  uses  the  diagonal  feet  alternately,  so  that  the  centre  of 
gravity  always  falls  within  the  quadrangle  formed  by  them,  and  near 
the  intersection  of  the  lines  connecting  their  diagonal  feet. 

The  theory  of  the  walk  in  quadrupeds  is  that  there  should  be 
two  feet  always  upon  the  ground  while  the  diagonal  ones  are  being 
advanced,  and  if  the  legs  moved  synchronously  in  pairs,  there  must  be 
four  on  the  ground  for  a  brief  time  at  each  step,  —  for  from  the  defi- 
nition of  the  walk  one  foot  does  not  rise  until  the  other  is  upon  the 
ground;  —  it  follows  that  in  two  pairs  of  feet  the  two  feet  cannot  rise 
until  the  other  two  are  upon  the  ground.  This,  one  would  think, 
should  be  proved  by  the  camera;  but  it  shows  that  sometimes  three 
feet  are  on  the  ground,  but  never  four  at  the  same  time.  How  is 
this  ?  Is  the  definition  of  the  walk  incorrect  ?  It  is  so  when  applied 
to  quadrupeds.  In  fact,  the  diagonal  limbs  do  not  act  synchronously 
in  the  slow  movements  of  the  walk,  for  it  is  more  difficult  to  maintain 
an  equilibrium  in  a  slow  movement  than  a  fast,  —  as  a  top  falls  when 
its  revolutions  are  slow,  —  and  for  the  reason  that  a  horse  never  rests 
on  two  legs,  but  always  on  the  two  anterior  and  one  posterior,  so 
that  the  centre  of  gravity  always  falls  within  a  triangle ;  so  in  the 
walk  one  of  the  reserve  feet  holds  the  ground  for  a  brief  time  until 
the  other  has  the  start,  in  order  to  shorten  the  time  in  which  the 
centre  of  gravity  has  but  two  points  of  support. 

The  walk,  being  the  slowest  pace  of  the  horse,  has  been  best 
observed  and  most  discussed,  but  chiefly  as  to  the  order  in  which  the 
feet  are  moved.  There  can  be  little  doubt  that  habit  in  the  horse,  as 
in  man,  determines  which  foot  shall  be  the  first  to  move ;  and  it  may 
often  be  determined  by.  their  accidental  relation  to  each  other  at  the 
instant  that  he  has  occasion  to  move  one  of  them,  though  it  would 
be  doing  no  injustice  to  the  brute  to  suppose  him  to  have  a  suffi- 
cient freedom  of  will  to  choose  which  foot  he  should  put  forward 
if  he  waited  to  think  of  it. 

When  the  horse  quickens  his  walk,  he  does  not  at  once  change  his 
pace,  but  extends  his  strides  and  makes  them  more  uniform,  until 
further  extension  becomes  difficult,  when  he  will  break  into  a  trot,  in 
which  there  are  never  more  than  two  feet  upon  the  ground  at  a  time, 


THE    HORSE    IN    MOTION.  I  17 

as  has  been  already  stated.      This  change  from  a  walk  to  a  trot  is 
shown  in  the  fine  silhouette  (Plate  XLI.). 

Single-foot  is  an  irregular  pace,  rather  rare,  and  distinguished  by 
the  posterior  extremities  moving  in  the  order  of  the  fast  walk  and  the 
anterior  ones  in  that  of  a  slow  trot.  These  mixed  paces  are  quite 
compatible,  as  they  are  of  the  same  kind  and  move  in  the  same  diago- 
nal order.  It  is  illustrated  by  Plate  LV.  The  rhythm  of  the  foot- 
falls is  characteristic,  and  once  heard  will  ever  after  be  recognized, 
even  in  the  dark.  The  same  horse  is  made  to  illustrate  the  regular 
walk  in  Plate  L. 


CHAPTER   VII. 


ILLUSTRATIONS  OF  THE  PACES. 

THE  series  of  plates  which  follow  are  intended  to  show  more  fully 
than  was  possible  in  the  silhouettes  that  precede  them,  the  action  of 
the  horse  in  every  possible  position  in  all  the  paces ;  they  require, 
however,  a  brief  explanation. 

The  same  ground  was  used  as  that  on  which  all  the  experiments 
were  made  that  are  detailed  in  the  Appendix ;  but  instead  of  a  full 
battery  of  twenty-four  cameras,  only  five  were  employed,  and  they  were 
arranged  in  the  manner  shown  in  Plate  I.  (frontispiece).  One  only 
represented  the  battery,  and  that  was  in  the  middle  of  the  series ;  the 
other  four  were  placed  at  nearly  equal  distances,  two  on  each  side,  so 
as  to  represent  the  arc  of  a  circle  whose  centre  should  be  occupied 
by  the  horse  at  the  moment  he  appeared  opposite  the  central  of  the 
five  cameras.  At  this  point  a  thread  was  drawn  across  the  track 
which,  when  the  breast  of  the  horse  came  in  contact  with  it,  made 
magnetic  communication  with  all  five  of  the  cameras  at  the  same 
instant,  so  that  five  views  of  the  animal  were  produced  at  the  same 
time,  showing  him  from  as  many  different  directions. 

The  time  of  exposure  of  the  negatives  was  so  immeasurably  small 
that  few  of  the  pictures  taken  were  perfect  in  all  the  details ;  and  as 
red  appears  as  black  in  the  photograph,  so  all  bay  horses  were  without 
any  details  of  light  and  shade,  simply  as  silhouettes ;  and  even  when 
the  horse  was  light  or  gray  there  would  be  some  defect  in  some  part 
of  every  one  of  the  series. 

Experiments  were  made  with  various  processes  to  reproduce  them 
with  all  their  defects;  but  it  was  found  that  the  making  of  tlu 


PLATE     LVI1 


JSTFA.TIONS   OF   THE    PA.CES.  RtJNKTNG. 


t 

-• 


ILL  I  iHSTG. 


•  :   :  : 


PLATK    LX 


ILLUSTRATIONS  OF  THE   PACES. 


*.*  • 


•;;:    r  A      ; 
:  t.tt>'.  ••• 


ILLUSTRATIONS  OF  THE   FACES.    TROTTING. 


PLATE     LXV 


ILLUSTRATIONS   CF   THE    FA.CES.    RTJW1J  IN  G-. 


FLA', 


II/LUSTRA.TIO-NS  OF  THE   PACES.      WALKlTsTG-. 


- 


ILLUSTRATIONS  OF  THE   PACES.    TROTTING- 


ILLUSTRATIONS  OF  THE   PACES.   AMBLING-. 


L20CV. 


CP    THE    PAC  E  3 .    P/-.FI,'  '.IN"O. 


ILLUSTRATIONS    OF    THt 


:  iHG-. 


'.,-,:••:  :'/'••:•;:-  ; 


XXXI 


ILLUSTRATTOTS5S  OF  THE   PACES.  ..RXTTsTN INO. 


PLATE     LXXXtll 


ILLUSTRATIONS  OF  THE   PACES.     LEAPING. 


PLATE  LXXXIV 


ILLUSTRATIONS  OF  THE  PA.CES.  LEAPING-. 


LXXXV 


II/LUSTRATIOTSTS  OF  THE  PACES.  RtTtSTNTtTCr. 


PLATE   IX XXVI II 


ILLUSTRATIONS   OF  THE   PACES. 


PLATE.  LXXXIX 


ILLUSTRATIONS   CF   THE   PACE  3.  TROTTING-: 


' 


II/LUST  RATIONS  OF  THE   PACES.     RUMN IH G-. 


xrn 


ILLUSTRATIONS  OF  THE   PACES. 


:i.E    PACKS. 


PLMTE    XCV 


ILLUSTRATIONS   OF  THE   PACES     WALKING-. 


XCVT 


^ILLUSTRATIONS  OF  THE   PACES.     RUNNING-. 


.ILLUSTRATIONS  OF  THE   PACES.     CANTER. 


PLATE  VCIX 


II/LUSTRATIOKS  OF  THE  PACES.    LEAPING. 


•  •  :  :     :  •' 
•::..:.- 


ILL/US  THAI' IONS    OF   THE    PACES.    ABOUT  TO  I_tAP. 


Cl 


ILLUSTRATIONS  OF  THE   PACES.  LEAPING. 


PLATE     CIII 


ILLUSTRATIONS   OF  THE   PA.CE3.    RAPID   "WALK. 


PLATE     CIV 


<f\. 

ni 


• 


ILLUSTRATIONS   OF  THE    PACES.    'RtnSTNTN'G 


ILLUSTRATIONS   OF   THE    PACES     WALKING-. 


THE    IIORSK    IN    MOTION.  I  19 

necessary  transfers  from  the  originals,  while  they  reproduced  accu- 
rately all  the  defects  of  the  original  photographs,  reproduced  them 
with  diminished  sharpness,  and  these  methods  were  abandoned. 
Under  the  direction  of  the  Heliotype  Printing  Company  another 
plan  was  adopted.  From  the  original  photographs,  by  the  helio- 
type process,  copies  were  produced  on  gelatine  magnified,  and  prints 
taken  on  Bristol  board  in  blue  ink  in  the  same  manner  as 
in  the  ordinary  heliotype  process.  These  prints,  with  the  originals, 
were  put  into  the  hands  of  artists  skilled  in  drawing  on  wood  for 
engravers,  who  drew  them  with  a  pen  in  india  ink,  under  careful 
supervision  of  the  writer,  so  as  to  preserve  the  outlines  as  they  were 
rendered  by  the  camera  and  avoid  reproducing  the  blotted  defects 
of  the  originals.  These  drawings  were  then  reproduced  on  stone  by 
the  camera,  reduced  to  their  original  size,  and  the  prints  given  in  the 
volume  were  printed  from  these  stones  as  in  ordinary  lithography. 

They  cannot  fail  to  be  of  great  advantage  to  artists,  especially 
those  who  would  perfect  themselves  in  animal  drawing,  and  that 
acknowledged  difficult  branch  of  their  art,  —  animals  in  motion. 

They  and  the  public  generally  are  greatly  indebted  to  Mr.  Stanford 
for  the  enlightened  liberality  with  which  he  has  pursued  this  costly 
investigation,  and  given  its  results  to  the  public  without  any  prospect 
of  pecuniary  advantage  to  himself. 

It  will  be  observed  that  some  of  these  pictures  are  so  nearly  alike 
that  at  a  superficial  view  they  appear  the  same ;  but  it  is  almost  impos- 
sible that  the  times  in  which  any  two  should  be  photographed  should 
coincide,  and  there  will  be  found  no  two  exactly  alike ;  and  the  near 
approach  to  the  same  posture  proves  the  universality  of  the  law  in 
which  all  the  paces  are  performed. 

In  some  of  these  plates  there  are  but  four  pictures;  the  fifth,  owing 
to  some  serious  defect  or  failure  of  the  apparatus  altogether,  is 
wanting. 

Plate  LVII.  represents  a  position  in  the  run  corresponding  with 

that  in  Fig.  n,  page  95,  differing  only  in  the  fact  that  the  right  fore 

N   performing  its  functions   rather  than  the  left,  as  in  the  cut. 

From  this  extremity  the  body  will   be  projected   from  the   ground, 


I2O 


THE    HORSE    IN    MOTION. 


and  the  diagonal  hind  is  advancing  to  the  support  of  the  centre  of 
gravity.  Comparing  this  with  Plate  LXV.,  in  which  one  figure  is 
wanting,  the  correspondence  will  be  found  so  close  that  at  first  sight 
it  is  difficult  to  convince  one's  self  that  they  are  not  identical  pic- 
tures ;  but  on  careful  inspection  it  will  be  perceived  that  in  the 
quartette  the  body  is  less  advanced  and  the  supporting  leg  is  farther 
from  the  perpendicular.  The  missing  picture  should  be  the  first 
in  the  regular  order. 

Comparing  again  this  plate  with  Plate  CII.,  the  body  of  the  horse 
will  be  found  to  have  advanced  from  the  position  in  the  former  until 
the  supporting  leg  is  quite  perpendicular,  and  the  other  limbs  are 
relatively  advanced. 

In  Plate  CIV.  there  is  still  further  advance;  the  foot  is  under 
the  centre  of  gravity,  and  the  posterior  extremities  are  being  gath- 
ered under  the  body  in  the  order  with  which  they  will  successively 
take  their  turn. 

Plate  LXXVIII.  exhibits  the  same  movement  on  the  instant  that 
the  propulsive  effort  of  the  limb  is  concluded  and  the  foot  is  leav- 
ing the  ground.  From  this  last  position  there  is  an  interval  of  one 
fifth  of  a  stride,  in  which  there  is  no  support  given  to  the  weight 
of  the  body,  but  it  is  moving  as  a  projectile  until  the  diagonal  hind 
foot  reaches  the  ground,  which  it  is  about  to  do  in  the  following 
plate.  The  left  hind  foot  will  be  the  first  to  make  the  contact,  from 
which  we  know  that  the  right  fore  foot  was  the  one  by  which  the 
body  had  been  projected  into  the  air ;  the  right  hind  foot  will  follow 
and  take  the  ground  a  step  farther  in  advance.  This  plate  may  be 
compared  with  LXX.,  in  which  the  right  feet  are  in  corresponding 
positions  with  the  left,  as  seen  in  the  former.  Plate  XC.  represents 
the  horse  in  a  similar  position. 

The  slow  trot  is  shown  in  Plate  LIX.,  and  is  not  distinguishable 
from  the  fast  walk,  as  seen  in  the  succeeding  plate ;  it  is  only  when 
the  instant  of  exposure  of  the  sensitive  plate  of  the  camera  is  coin- 
cident with  that  in  which  all  the  feet  are  off  the  ground  that  the 
walk  can  be  distinguished  from  the  slow  trot. 

Plate  LXI.  is  also  an  attitude  of  the  trot,  but  it  is  recognized  by 


THE    HORSE    IN    MOTION.  121 

the  higher  action  of  the  free  limbs,  and  this  action  indicates  a  higher 
rate  of  speed  than  is  possible  in  the  walk. 

In  the  succeeding  plate  the  walk  is  again  represented  and  is  un- 
;kable,  as  the  three  feet  are  supporting  weight,  as  indicated 
both  by  their  position  and  the  yielding  of  the  pasterns. 

In  Plate  LXIII.  we  see  the  sluggish  run  in  which  the  speed  or 
momentum  of  the  horse  does  not  permit  the  propulsion  of  the  fore 
to  carry  the  body  clear  of  the  ground  before  the  hind  ones  come 
to  the  support  of  the  centre  of  gravity  prematurely,  and  which  con- 
stitutes the  pace  known  as  the  canter.  (See  page  103.) 

The  fast  trot  is  shown  in  Plate  LXIV.  Plate  LXVI.  seems  to 
be  a  fast  walk,  in  which  the  groom  is  urging  the  horse  into  a  trot. 
The  position  may  be  interpreted  into  either  a  walk  or  a  trot. 

Plate  LXVI  I.  represents  a  position  in  the  leap,  and  is  fully  ex- 
plained in  the  sixth  chapter. 

The  walk  is  further  illustrated  in  the  two  following  plates. 

In  Plate  LXXI.  a  position  in  the  trot  is  shown  where  the  feet 
arc  all  clear  of  the  ground.  Before  the  fore  leg,  which  is  extending 
forward  to  reach  the  ground,  makes  the  contact,  it  must  be  straight- 
ened and  the  toes  raised,  as  in  Plate  LXIV.  As  already  stated,  it 
is  difficult  in  some  of  the  "Illustrations"  to  determine  a  slow  trot 
from  a  fast  walk,  for  there  may  be  an  instant  of  time  in  the  trot 
when  three  feet  are  on  the  ground.  The  mechanical  action  is  the 
same  in  both  paces,  and  the  distinction  is  based  on  the  speed.  This 
difficulty  could  not  occur  where  the  reader  has  the  advantage  of  a 
consecutive  series  of  views,  as  is  shown  in  Plate  L. 

The  heavy  Clydesdale  in  Plate  LXXI  I.  is  shown  in  the  am- 
bling pace  in  which  the  weight  of  the  body  is  borne  and  the  propul- 
sion performed  by  the  two  extremities  of  the  same  side. 

The  canter  is  illustrated  in  Plate  LXXVIII.  The  support  is 
here  given  by  the  left  fore  leg,  and  the  greater  flexion  of  the  diag- 
onal right  indicates  that  it  is  the  next  in  order  to  perform  that  func- 
tion. The  degree  of  action  indicates  a  low  rate  of  speed,  which 
could  be  attained  in  the  trot  with  greater  ease  to  the  horse  if  not 
to  his  rider. 

16 


122 


THE    HORSE    IN    MOTION. 


Plate  LXXXI.  represents  the  animal  in  the  greatest  degree  of 
extension  he  reaches  in  the  run.  The  posterior  extremities  have  suc- 
cessively performed  their  functions  as  supporters  and  propellers,  the 
anterior  limbs  are  extended  to  relieve  them,  and  for  the  instant 
the  diagonal  feet  are  upon  the  ground,  but  it  is  only  for  an  instant ; 
the  weight  of  the  body  is  already  on  the  fore  leg,  and  the  only  pro- 
pulsive force  left  in  the  hind  one  is  derived  from  the  reaction  of  the 
suspensory  ligament  and  its  reinforcing  tendons.  This  position 
nearly  corresponds  with  that  in  Fig.  8,  page  93,  though  a  little  in 
advance  of  it. 

Plate  LXXXV.  illustrates  the  run  in  the  position  shown  in  Fig. 
10,  page  95.  The  fore  leg  must  be  straight  from  the  elbow  to  the 
foot  when  it  makes  contact  with  the  ground,  as  only  in  that  rela- 
tion of  the  bones  forming  the  columns  of  support  could  the  weight 
suddenly  thrown  upon  them  be  borne.  A  moment's  consideration  of 
the  mechanical  construction  of  the  knee-joint  will  suffice  to  convince 
one  of  this,  and  a  weakness  at  that  point  which  renders  the  animal 
liable  to  stumble  is  a  very  serious  defect,  and  where  it  exists  it  in- 
dicates the  loss  of  the  balance  of  power  between  the  flexors  and 
extensors  of  the  foot.  This  inflexible  position  of  the  knee-joint  will 
be  found  to  be  universal  in  all  the  paces  when  the  limb  is  sustain- 
ing weight. 


u 

I 

W 

cu 


APPENDIX. 


, 


Tin:  following  account  of  the  methods  by  which  the  original 
holographs  were  produced  that  served  as  the  basis  of  the  analysis  of 
the  paces,  the  results  of  which  arc  contained  in  this  volume,  was 
furnished  by  Mr.  E.  J.  Muybridge,  the  photographer  by  whom  they 
were  executed. 

Some  time  in  1872  Mr.  Stanford,  being  desirous  of  settling  some 
controverted  questions  as  to  the  action  of  the  trotting  horse,  conceived 
the  idea  that  the  camera  might  be  made  available  for  that  purpose. 
To  this  end  he  consulted  with  Mr.  Muybridge,  and  induced  him  to 
undertake  some  experiments  in  instantaneous  photography.*  The 
experiments  made  at  that  time  were  inconclusive,  and  for  several 
years.  Mr.  Muybridge  being  absent  from  the  State,  the  matter  rested, 
though  it  was  not  abandoned  by  Mr.  Stanford. 

In  1877,  Mr.  Muybridge  having  returned,  the  experiments  were 
renewed.  A  few  pictures  were  taken  of  "  Occident "  while  in  motion 
—  a  noted  trotter,  owned  by  Mr.  Stanford  —  with  a  single  camera; 
and  one  of  these,  representing  him  with  all  his  feet  clear  of  the 
ground,  was  enlarged,  retouched,  and  distributed  among  various 
parties  interested. 

•  Instantaneous  pictures  were  defined  to  be,  at  that  time,  in  ordinary  photographic  par- 
lance, when  the  exposure  has  been  very  brief,  or  under  half  a  second.  In  the  liritish  Journal 
Photographic  Almanack  for  1868  it  is  stated  that  good  street  views  had  been  taken  in  a  twelfth 
part  of  a  second.  The  conditions,  as  there  given,  for  extreme  rapidity  of  exposure  are  a  good 
and  quick-acting  shutter,  a  lens  with  a  large  angular  aperture,  and  chemicals  in  perfect 
condition. 


124 


APPENDIX. 


The  result  of  this  experiment  was  so  successful  that  Mr.  Stanford 
determined  to  try  another  one  on  a  more  extended  scale.  He 
assumed,  if  one  picture  could  be  taken  instantaneously,  why  not  an 
indefinite  number,  and  by  increasing  the  number  of  cameras  increase 
to  the  same  extent  the  number  of  views,  and  illustrate  the  various 
positions  in  an  entire  stride  ? 

Mr.  Muybridge  was  authorized  to  procure  the  needed  apparatus, 
and  a  building  suitable  to  the  purpose  was  erected  on  the  west  side  of 
Mr.  Stanford's  private  track  at  Palo  Alto  (see  frontispiece).  In  the 
following  year,  1878,  the  preparations  were  complete;  every  resource 
of  the  photographic  art  had  been  provided  that  was  thought  to  be 
required  or  attainable.  Twelve  cameras  were  placed  in  the  building 
at  intervals  of  twenty-one  inches,  with  double  shutters  to  each.  These 
shutters  were  arranged,  one  above  and  the  other  below  the  opening 
through  which  light  was  admitted  to  the  lens,  and  held  by  india-rubber 
springs,  constructed  in  the  form  of  a  ring,  with  a  lifting  power  of  one 
hundred  pounds,  and  secured  by  latches,  to  be  liberated  on  the  com- 
pletion of  a  magnetic  current.* 

For  the  purpose  of  making  the  exposures  at  the  proper  intervals 
of  time,  a  machine  was  constructed  on  the  principle  of  a  Swiss  music- 
box,  having  a  cylinder  with  a  row  of  twelve  pins  arranged  spirally. 
This  was  put  in  motion  by  a  spring,  and,  as  it  revolved,  each  pin  in 
succession  established  a  magnetic  circuit,  with  the  magnet  connected 
with  each  of  the  twelve  cameras  in  succession,  and  the  whole  series  of 
exposures  was  made  in  the  time  occupied  by  a  single  complete  stride 
of  the  horse. 


*  This  description  of  the  shutters  and  their  mode  of  action  is  somewhat  obscure.  The 
shutter,  as  described  by  Kleffel  (Handbuch  der  Practischen  Photographic,  Leipzig,  1874,  p.  201), 
is  as  nearly  as  possible  the  double  shutter  used  by  Muybridge.  Kleffel's  shutter  was  held  by 
a  spring,  and  when  the  picture  was  to  be  taken  the  spring  was  touched,  and  the  shutter,  which 
had  an  opening  through  its  centre,  dropped  past  the  lens,  exposing  the  lens  to  the  light  during 
the  time  of  the  passage  of  the  opening  across  it.  He  recommended  weights  to  be  used  when 
greater  rapidity  was  required.  Muybridge's  modification  of  this  consisted  in  the  use  of  rubber 
springs  in  lieu  of  weights  as  recommended  by  Kleffel ;  though  no  claim  is  set  up  by  him  to 
priority  in  the  use  of  rubber  springs,  as  one  Thomas  Skaife  obtained  a  patent  in  England  for 
rubber  springs  for  camera  shutters  as  early  as  1856. 


X 


X 
H 


O 
pu 

cn 
H 

S 


o 


ff 

K 


U- 

O 


125 

This  arrangement  gave  the  attitude  of  the  horse  as  he  arrived 
before  each  of  the  cameras  in  succession  at  the  instant  of  exposure  of 
the  negatives.  In  practice  it  was  found  to  be  extremely  difficult  to 

the  apparatus  in  motion  at  the  exact  time  required,  and  to  regulate 
it  to  correspond  to  the  speed  of  the  horse. 

This  contrivance  was  found  to  be  best  adapted  to  the  more  irreg- 
ular movements  of  other  animals,  as  the  running  of  dogs,  the  flight  of 
birds,  feats  of  acrobats,  etc.  It  was  desirable  to  find  some  method 
that  would  better  represent  the  regular  movements  of  the  horse,  and 
which  should  be  regulated  by  his  own  movements. 

On  the  side  of  the  track  opposite  the  building  where  the  cameras 
were  placed,  and  in  such  position  as  to  receive  the  best  exposure  to 
light,  a  wooden  frame  was  erected,  about  fifty  feet  long  and  fifteen 
high,  at  a  suitable  angle,  and  covered  with  white  cotton  sheeting 
(Plate  CVII.),  divided  by  vertical  lines  into  spaces  of  twenty-one  inches, 
each  space  being  consecutively  numbered.  Eighteen  inches  in  front 
of  this  background  was  placed  a  base-board  twelve  inches  high,  and 
on  which  were  drawn  longitudinal  lines  four  inches  apart.  In  front 
of  this  base-board  a  strip  of  wood  was  fastened  to  the  ground,  upon 
the  top  of  which  wires  were  secured  at  an  elevation  of  about  an  inch 
above  the  ground  and  extending  across  the  track.  The  wire  was 
exposed  in  a  groove  to  one  only  of  the  wheels  of  the  sulky,  being 
protected  from  contact  with  the  horse's  feet  and  the  other  wheel. 
Each  wire  was  held  in  proper  tension  by  a  spring  on  the  back  of  the 
base-board,  so  arranged  that  when  the  wire  crossing  the  track  was 
depressed  by  the  wheel  it  should  draw  upon  the  spring  connected 
with  it,  and  make  contact  with  a  metallic  button  and  complete  the 
electric  circuit. 

These  wires  were  placed  at  distances  from  each  other  correspond- 
ing with  the  cameras  on  the  opposite  side  of  the  track,  and  with  the 
spaces  between  the  lines  drawn  on  the  background. 

From  this  description  it  will  be  readily  seen  that  the  depression  of 
the  first  wire  would  complete  the  circuit  and  cause  the  magnet  con- 
nected with  the  corresponding  camera  to  move  the  latch  and  liberate 
the  shutters,  exposing  the  sensitive  plate  for  a  space  of  time  that  is 


I26  APPENDIX. 

hardly  conceivable.  In  like  manner,  as  the  wheel  passed  over  the 
second  wire,  the  shutters  would  be  liberated  on  the  second  camera,  and 
so  on  until  the  whole  series  were  discharged.  When  the  horse  passed 
with  great  velocity  over  the  wires  these  shutters  were  discharged  with 
such  force  and  rapidity  that  the  horse  was  not  unfrequently  startled 
and  broke  his  gait. 

If  everything  was  properly  arranged  the  driver  had  but  to  keep  the 
wheel  of  his  sulky  in  the  groove  which  was  sunken  for  it,  and  it 
would,  by  depressing  the  wires  successively,  take  the  pictures  at  every 
twenty-one  inches  until  the  whole  series  were  taken. 

The  method  just  described  was  used  in  all  cases  where  horses  were 
driven  to  sulkies ;  but  when  wheels  were  not  used  this  arrangement 
with  wires  under  the  track  had  to  be  modified,  and  a  thread  was 
drawn  across  sufficiently  high  to  come  in  contact  with  the  horse's 
breast,  and  strong  enough  to  cause  the  contact  and  establish  the 
circuit  as  before,  but  not  so  strong  as  to  wound  the  horse  when 
going  at  full  speed. 

By  these  methods  many  views  were  taken  and  distributed  to  all 
parts  of  the  country :  they  attracted  a  great  deal  of  attention,  and 
elicited  a  great  variety  of  opinions  and  not  a  little  ridicule ;  some 
artistic  persons  displayed  great  ingenuity  in  burlesque,  —  no  one  under- 
stood them. 

The  number  of  cameras  was  afterwards  doubled,  and  they  were 
placed  at  intervals  of  twelve  inches  to  still  closer  analyze  the  move- 
ments of  the  horse.  Lines  were  drawn  across  the  track  at  correspond- 
ing distances,  and  the  numbers  indicating  them,  instead  of  being  at 
the  base  of  the  screen,  were  on  a  board  between  the  horse  and  the 
cameras.  The  heliotype  plates  Nos.  CVI.  and  CVII.  represent  the 
battery  of  cameras  and  the  screen  as  they  were  when  twenty-four 
cameras  were  in  position. 

The  whole  of  the  series  of  twenty-four  figures  each  used  in  this 
volume  to  illustrate  the  paces  were  taken  in  this  manner.  They  were 
very  accurately  taken,  and  are  specimens  of  the  best  results  attained 
after  years  of  expensive  experience ;  and  the  heliotypes  are  perfect 
transcripts  of  the  original  photographs. 


APPENDIX.  127 

It  will  readily  be  understood  that  the  accuracy  of  these  analyses 
upon  the  uniform  tension  and  strength  of  the  threads  con- 
nected with  the  springs  through  which  the  circuit  is  formed.  The 
perfection  of  the  pictures  depends  upon  the  sensitiveness  of  the  chem- 
icals and  the  time  occupied  in  their  exposure  to  light.  This  time  is 
as  nearly  instantaneous  as  can  well  be  conceived.  Mr.  Muybridge 
estimates  it  by  comparing  the  enlargement  of  the  horizontal  diameter 
of  an  object  photographed  with  the  vertical  diameter  of  the  same 
object  at  one  five-thousandth  of  a  second.  This  can  only  be  deter- 
mined by  measurement,  and  that  approximately  even  in  objects  of 
considerable  size ;  it  is  so  nearly  instantaneous  that  there  is  no 
appreciable  loss  of  proportions  from  differences  between  vertical  and 
horizontal  diameters. 


University  Press:  John  Wilson  &  Son,  Cambridge. 


14  DAY  USE 

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